Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This U.S. non-provisional patent application claims priority under 35 U.S.C. §119 of Korean Patent Application No. 10-2014-0066879, filed on Jun. 2, 2014, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention disclosed herein relates to an amplifier circuit, and more particularly, to a current-voltage conversion amplifier circuit. 
         [0003]    An amplifier circuit means an electronic circuit amplifying the voltage, current, and power of an input signal to generate an output signal. The amplifier circuit includes a voltage amplifier circuit, a current amplifier circuit, a power amplifier circuit, and a current-voltage amplifier circuit converting current signal into voltage signal and amplifying it. 
         [0004]    A high-impedance preamplifier and a transimpedance amplifier are mainly used as the current-voltage conversion amplifier circuit. The high-impedance preamplifier improves the reception sensitivity by increasing a load resistance to increase an input voltage. The transimpedance amplifier uses a resistance in a feedback loop. The thermal noise of the transimpedance amplifier is reduced by the resistance. Additionally, the transimpedance amplifier has a more improved dynamic range compared to the high-impedance preamplifier. 
         [0005]    However, the transimpedance amplifier requires a resistance of hundreds of ohms to process a small current signal. Therefore, when the transimpedance amplifier is used in the current-voltage conversion amplifier circuit, its power consumption is high and its circuit area is increased. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a current-voltage conversion amplifier circuit reducing power consumption and circuit area. 
         [0007]    Embodiments of the present invention provide current-voltage conversion amplifier circuits including: a plurality of light receiving devices generating a current signal proportional to an amount of light by receiving the light; a plurality of multipliers amplifying the current signal, converting the amplified current signal into a first voltage signal, outputting the amplified current signal, or outputting the converted first voltage signal; a plurality of multi input amplifiers outputting first and second output voltage pairs through a process for receiving output values of the plurality of multipliers and an offset voltage and amplifying the received output values and offset voltage; a multiplexing unit selecting and outputting one first and second output voltage pair among the first and second output voltage pairs outputted from the plurality of multi input amplifiers; and a signal conversion unit converting a difference value between first and second output voltages outputted from the multiplexing unit and outputting the converted digital signal. 
         [0008]    In some embodiments, the signal conversion unit may change an output range of the digital signal outputted from the signal conversion unit according to a magnitude of the offset voltage. 
         [0009]    In other embodiments of the present invention, multipliers include: a bias terminal applying a bias current to a first node; a start-up unit connected between the first node and a power terminal and applying an additional current to the first node; a reference voltage generation unit connected between a second node and a ground terminal and maintaining a voltage constantly between the second node and the ground terminal; a discharging unit connected between a third node and the ground terminal and discharging a voltage of the third node; a current offset removal unit connected between the power terminal and the second node and removing a dark current outputted even when light is not incident to a light receiving device; a current signal amplifier unit connected between the power terminal and an output terminal and amplifying a current signal outputted from the light receiving device and outputting the amplified current signal; and a current-voltage selection unit connected to a fourth node and converting the amplified current signal into a first voltage signal according to a conversion signal, wherein the light receiving device is connected to the third node. 
         [0010]    In some embodiments, the start-up unit may include a first switch connected to the first node and a first start-up transistor diode-connected between the first switch and the power terminal, wherein the first switch may apply the additional current applied through the first start-up transistor to the first node according to a first switching signal applied to a gate terminal. 
         [0011]    In other embodiments, the reference voltage generation unit may include a first reference voltage generation transistor connected between the second and third nodes and a second reference voltage generation transistor connected between the first node and the ground terminal, wherein the first reference voltage transistor may be turned-on by the first node voltage applied to the gate terminal and may apply to the third node a current signal having the same magnitude as the current signal outputted from the light receiving device. 
         [0012]    In still other embodiments, the second reference voltage generation transistor may be turned-on by the third node voltage applied to a gate terminal and may maintain voltages of the first and third nodes constantly by discharging a voltage of the first node. 
         [0013]    In even other embodiments, the discharging unit may include a discharge transistor diode-connected to the third node and a discharging switch connected between the discharging transistor and the ground terminal, wherein the discharging switch may apply a third node voltage applied to the discharging transistor to the ground terminal according to a discharging signal applied to a gate terminal. 
         [0014]    In yet other embodiments, the current offset removal unit may include a plurality of dark current removal switches connected to the first node and a plurality of current sources connected between the plurality of dark current removal switches and the power terminal, wherein at least one dark current removal switch connected to at least one current source activated proportional to a magnitude of the dark current outputted from the light receiving device may be turned-on. 
         [0015]    In further embodiments, a current having a magnitude identical or similar to that of the dark current may flow in the at least one activated current source. 
         [0016]    In still further embodiments, the current signal amplifier unit may include: a first current mirror transistor connected between the power terminal and the second node; a second current mirror transistor having a gate terminal connected to a drain terminal of the first current mirror transistor; a plurality of amplification switches connected between the fourth node and the output terminal; and a plurality of current signal amplification transistors connected between the plurality of amplification switches and the power terminal and having gate terminals connected to a gate terminal of the first current mirror transistor. 
         [0017]    In even further embodiments, a gate voltage having the same magnitude as the first current mirror transistor may be applied to each of the second current mirror transistor and the plurality of current signal amplification transistors; a magnitude of the current signal amplified may be determined by a ratio of a size with respect to the first current mirror transistor; and at least one amplification switch connected at least one activated current signal amplification transistor may be turned-on. 
         [0018]    In yet further embodiments, the signal conversion unit may include a conversion switch connected to the fourth node and a resistor connected between the conversion switch and the ground terminal; when turned-off by the conversion signal applied to a gate terminal, the conversion switch may output the amplified current signal an output terminal; and when turned-on by the conversion signal, the conversion switch may convert the amplified current signal into the first voltage signal by the resistor and may output the converted first voltage signal. 
         [0019]    In still other embodiments of the present invention, multi input amplifiers include: an input terminal receiving a current signal or a first voltage signal; a first amplifier unit converting signals applied from the input terminal and the offset terminal into first and second sampling voltages and outputting the converted first and second sampling voltages; a second amplifier unit converting signals inputted from the input terminal and a common terminal into third and fourth sampling voltages and outputting the converted third and fourth sampling voltages; a differential amplifier receiving the first and second sampling voltages and converting the received first and second sampling voltages into a first output voltage to output the converted first output voltage, and receiving the third and fourth sampling voltages and converting the received third and fourth sampling voltages into a second output voltage to output the converted second output voltage; a first output unit connected between the differential amplifier and a first output terminal and amplifying the first output voltage by a predetermined gain to output the amplified first output voltage to the first output terminal; and a second output unit connected between the differential amplifier and a second output terminal and amplifying the second output voltage by the predetermined gain to output the amplified second output voltage to the second output terminal. 
         [0020]    In some embodiments, the first amplifier unit may include: a first reset switch connected to a first node and applying a common mode voltage to the first node according to a first and second reset signal applied to a gate terminal; a first switch connected between the first node and a second node and applying the amplified current signal and the first voltage signal applied from the input terminal to the second node according to a first initial value sampling signal applied to the gate terminal; a first capacitor connected to the second node and charged by the amplified current signal and the first voltage signal; a second switch connected to a third node and applying an offset voltage applied from the offset terminal to the third node according to a first data sampling signal applied to the gate terminal; a second capacitor connected to the third node and charged by the offset voltage; a third switch connected between the second node and the third node and turned-on or turned-off according to an amplification mode signal applied to the gate terminal; a fourth switch connected to a fourth node and applying the common mode voltage to the fourth node according to a second initial value sampling signal applied to the gate terminal; a fifth switch connected to a fifth node and applying the common mode voltage to the fifth node according to a second data sampling signal applied to the gate terminal; a sixth switch connected to the fourth node and applying the sampling voltage outputted from the first capacitor to the first differential amplifier and the first amplifier unit according to the amplification mode signal applied to the gate terminal; and a seventh switch connected to the fifth node and applying the second sampling voltage outputted from the second capacitor to the differential amplifier according to the amplification mode signal applied to the gate terminal. 
         [0021]    In other embodiments, the first output unit may include: a third capacitor connected to a sixth node and determining a gain of a first output voltage according to a ratio of the sum of capacities of the first and second capacitors; an eighth switch connected to the six node and applying the common mode voltage to the third capacitor according to a first sampling mode signal applied to the gate terminal; and a ninth switch connected to the third capacitor and applying the common mode voltage to the third capacitor according to a second sampling mode signal applied to the gate terminal. 
         [0022]    In still other embodiments, a first output terminal may be connected to the sixth node; the first output voltage may be outputted through the first output terminal; and a gain of the first output voltage may be changed in proportion to a ratio of the sum of capacities of the first and second capacitors and a capacity of a third capacitor. 
         [0023]    In even other embodiments, the second amplifier unit may include: a second reset switch applying the common mode voltage to a seventh node according to the first and second reset signal; a tenth switch connected between the seventh node and an eighth node and applying the common mode voltage to the eighth node according to the first initial value sampling signal applied to the gate terminal; a 11th switch connected between the input terminal and a ninth node and applying the amplified current signal or the first voltage signal to the ninth node according to the first data sampling signal applied to the gate terminal; a fourth capacitor connected to the eighth node and charged by the common mode voltage; a fifth capacitor connected to the ninth node and charged by the amplified current signal or the first voltage signal; a 12th switch connected between the eighth node and the ninth node and turned-on or turned-off according to the amplification mode signal applied to the gate terminal; a 13th switch connected to a tenth node and applying the common mode voltage to the tenth node according the second initial value sampling signal applied to the gate terminal; a 14th switch connected between the tenth node and a 11th node and applying the common mode voltage to the 11th node according to the second data sampling signal applied to the gate terminal; a 15th switch connected to the tenth node and applying the fourth sampling voltage outputted from the fourth capacitor to the differential amplifier and the second output unit according to the amplification mode signal applied to the gate terminal; and a 16th switch connected between the 11th node and the differential amplifier and outputting the fifth sampling voltage outputted from the fifth capacitor to the differential amplifier according to the amplification mode signal applied to the gate terminal. 
         [0024]    In yet other embodiments, the second output unit may include: a sixth capacitor connected to a 12th node and determining a gain of a second output voltage according to a capacity ratio with respect to the fifth capacitor; a 17th switch connected to the 12th node and applying the common mode voltage to the sixth capacitor according to the first sampling mode signal applied to the gate terminal; and an 18th switch connected to the sixth capacitor and applying the common mode voltage to the sixth capacitor according to the second sampling mode signal. 
         [0025]    In further embodiments, a second output terminal may be connected to the 12th node; the second output voltage may be outputted through the second output terminal; and a gain of the second output voltage may be changed proportional to a ratio of the sum of capacities of the fourth and fifth capacitors and a capacity of the sixth capacitor. 
         [0026]    In still further embodiments, when the first voltage signal is inputted to the input terminal, the first reset signal may be applied to the gate terminal of the first and second reset switch; when the amplified current signal is inputted to the input terminal, the second reset signal may be applied to the gate terminal of the first and second reset switch; and the amplified current signal may have an initial voltage as the common mode voltage according to the second reset signal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    The accompanying drawings are included to provide a further understanding of the present invention, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present invention and, together with the description, serve to explain principles of the present invention. In the drawings: 
           [0028]      FIG. 1  is a block diagram illustrating a current-voltage conversion amplifier circuit according to an embodiment of the present invention; 
           [0029]      FIG. 2  is a circuit diagram illustrating a multiplier shown in  FIG. 1  according to an embodiment of the present invention; 
           [0030]      FIG. 3  is a circuit diagram illustrating a multi input amplifier shown in  FIG. 1  according to an embodiment of the present invention; and 
           [0031]      FIG. 4  is a signal diagram illustrating clock signals inputted to a multi input amplifier shown in  FIG. 3  according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0032]    Various modifications are possible in various embodiments of the present invention and specific embodiments are illustrated in drawings and related detailed descriptions are listed. Accordingly, the present invention is not intended to limit specific embodiments and is understood that it should include all modifications, equivalents, and substitutes within the scope and technical range of the present invention. 
         [0033]      FIG. 1  is a block diagram illustrating a current-voltage conversion amplifier circuit according to an embodiment of the present invention. Referring to  FIG. 1 , a current-voltage conversion amplifier circuit  100  includes first to nth light receiving devices PD 1  to PDn, a multiplier unit  110 , a multi input amplifier unit  120 , a multiplexing unit  130 , and an analog digital converter (ADC) unit  140 . 
         [0034]    The first to nth light receiving devices PD 1  to PDn, as a device converting optical signal into current signal, may include photodiodes and photo transistors. As light hits, the first to nth light receiving devices PD 1  to PDn generate electrons and positively charged holes and due to this, current signal is generated. The first to nth light receiving devices PD 1  to PDn apply the generated current signal to the multiplier unit  110 . 
         [0035]    The multiplier unit  110  includes first to nth multipliers  111  to  11   n . The first to nth multipliers  111  to  11   n  receive current signals from the first to nth light receiving devices PD 1  to PDn, respectively. The first to nth multipliers  111  to  11   n  amplify current signals. The first to nth multipliers  111  to  11   n  may operate in a current or voltage mode. When operating in a current mode, the first to nth multipliers  111  to  11   n  amplify current signals and then apply the amplified current signals to the multi input amplifier unit  120 . When operating in a voltage mode, the first to nth multipliers  111  to  11   n  amplify current signals and after converting the amplified current signals into first voltage signals, applies the converted first voltage signals to the multi input amplifier unit  120 . 
         [0036]    The multi input amplifier unit  120  includes first to nth multi input amplifiers AMP 1  to AMPn. An amplified current signal or a first voltage signal and an offset voltage VOS are applied to the first to nth multi input amplifiers AMP 1  to AMPn. 
         [0037]    When an amplified current signal and an offset voltage VOS are applied, the first to nth multi input amplifiers AMP 1  to AMPn convert them into voltage signals by adjusting a sampling time of a current signal. Through the adjustment of a sampling time, the amplification gain of an output voltage signal may vary. 
         [0038]    When a first voltage signal and an offset voltage VOS are applied, the first to nth multi input amplifiers AMP 1  to AMPn convert the first voltage signal into a second voltage signal. Since the first to nth multi input amplifiers AMP 1  to AMPn cannot adjust a sampling time for voltage signal, amplification according to a predetermined gain is possible only. 
         [0039]    The first to nth multi input amplifiers AMP 1  to AMPn apply first and second output signals VOUT 1  and VOUT 2  having phases complementary to each other to the multiplexing unit  130 . According to the size of an offset voltage VOS, a digital signal output range of the ADC unit  140  is determined. 
         [0040]    The multiplexing unit  130  receives a plurality of first and second output signals VOUT 1  and VOUT 2  from the multi input amplifier unit  120 . The multiplexing unit  130  may use an analog multiplexer. The multiplexing unit  130  selects one pair from the plurality of first and second output signals VOUT 1  and VOUT 2  and then applies it to the ADC unit  140 . 
         [0041]    The ADC unit  140  may use an analog-to-digital signal converter converting an analog signal into a digital signal. The ADC unit  140  obtains a difference value between first and second output signals VOUT 1  and VOUT 2  in one pair received from the multiplexing unit  130 . The ADC unit  140  converts the difference value into a 10-bit digital signal and outputs it. 
         [0042]    The current-voltage conversion amplifier circuit  100  amplifies current signals outputted from the first to nth light receiving devices PD 1  to PDn and convert the amplified current signals into voltage signals to output them. When a current signal amplified by the multiplier unit  110  is outputted to the multi input amplifier unit  120 , the multi input amplifier unit  120  may adjust an output gain through the sampling time adjustment of a current signal. 
         [0043]      FIG. 2  is a circuit diagram illustrating the multiplier shown in  FIG. 1  according to an embodiment of the present invention. The multiplier  200  of  FIG. 2  is a circuit diagram illustrating the first to nth multipliers  111  to  11   n  shown in  FIG. 1 . The multiplier  200  includes a start-up unit  210 , a reference voltage generation unit  220 , a discharging unit  230 , a current offset removal unit  240 , a current signal amplifier unit  250 , and a current-voltage selection unit  260 . 
         [0044]    Through a bias terminal IBIAS, a bias current is applied to a first node n 1 . The voltage of the first node n 1  becomes higher due to the bias current. When the voltage of the first node n 1  is increased to a certain degree, the reference voltage generation unit  220  may have a driving capability. In order to drive the reference voltage generation unit  220 , a first NMOS transistor MN 1  of the reference voltage generation unit  220  needs to be turned-on. However, since the magnitude of a bias current is small, the fast voltage rise of the first node n 1  is impossible. 
         [0045]    The start-up unit  210  helps the fast drive of the reference voltage generation unit  220 . The start-up unit  210  includes a first PMOS transistor MP 1  and a first switch SW 1 . In the first PMOS transistor MP 1 , a source terminal is connected to a power terminal VDD and a gate terminal and a drain terminal are diode-connected. A source terminal of the first switch SW 1  is connected to the drain terminal and the gate terminal of the first PMOS transistor MP 1  and a drain terminal of the first switch SW 1  is connected to the first node n 1 . 
         [0046]    The start-up unit  210  is driven by a first switching signal S 1  applied to the first switch SW 1 . The first switching signal S 1  has a first voltage level L 1  according to a high state and a second voltage level L 2  according to a low state. When the first NMOS transistor MN 1  of the reference voltage generation unit  220  is turned off, the first switching signal S 1  of the second voltage level L 2  is applied to the first switch SW 1 . Once the first switch SW 1  is turned-on, a current applied through the first PMOS transistor MP 1  is applied to the first node n 1 . Since the voltage of the first node n 1  rises faster compared to when a bias current is applied, the fast turn-on of the first NMOS transistor MN 1  is possible. 
         [0047]    When the first NMOS transistor MN 1  of the reference voltage generation unit  220  is turned off, the first switching signal S 1  of the second voltage level L 1  is applied to the first switch SW 1 . Once the first switch SW 1  is turned off, a current applied to the first node n 1  through the first PMOS transistor MP 1  may stop. Accordingly, the current consumption of the multiplier  200  may be reduced. 
         [0048]    The reference voltage generation unit  220  includes first and second NMOS transistors MN 1  and MN 2 . A gate terminal of the first NMOS transistor MN 1  is connected to the first node n 1 . A drain terminal of the first NMOS transistor MN 1  is connected to a second node n 2  and its source terminal is connected to a third node n 3 . A drain terminal of the second NMOS transistor MN 2  is connected to the first node n 1  and its source terminal is connected to a ground terminal. A gate terminal of the second NMOS transistor MN 2  is connected to a third node n 3 . A light receiving device PD is connected between the third node n 3  and the ground terminal. 
         [0049]    The first NMOS transistor MN 1  is turned-on by the voltage of the first node n 1  applied to its gate terminal. Once the first NMOS transistor MN 1  is turned-on, the start-up unit  210  stops driving. Once the start-up unit  210  stops driving, only voltage by a bias voltage is applied to the gate terminal of the first NMOS transistor MN 1 . 
         [0050]    When light is incident to the light receiving device PD, the reverse biased light receiving device PD applies a current signal to the ground terminal. No current pass is in the reference voltage generation unit  220 . Therefore, a current having the same magnitude as a current signal occurring in the light receiving device PD is applied to the second node n 2  through the second PMOS transistor MP 2 . Since the first NMOS transistor MN 1  is in a turned-on state, a current applied through the second PMOS transistor MP 2  is applied to the third node n 3 . 
         [0051]    Once the first NMOS transistor MN 1  is turned on, the voltage of the third node n 3  rises. A voltage is applied to the gate terminal of the second NMOS transistor MN 2  through the third node n 3  and the second NMOS transistor MN 2  is turned-on. The voltage of the first node n 1  raised by a bias current is discharged to the ground terminal through the second NMOS transistor MN 2 . Accordingly, the voltages of the first and third nodes n 1  and n 3  may be maintained as a reference voltage. 
         [0052]    The discharging unit  230  includes a third NMOS transistor MN 3  and a second switch SW 2 . A gate terminal and a drain terminal of the third NMOS transistor MN 3  are diode-connected to the third node n 3 . A source terminal of the third NMOS transistor MN 3  is connected to a drain terminal of the second switch SW 2 . A source terminal of the second switch SW 2  is connected to the ground terminal. A second switching signal S 2  is applied to a gate terminal of the second switch SW 2 . The second switching signal S 2  has a first voltage level L 1  according to a high state and a second voltage level L 2  according to a low state. 
         [0053]    As the first NMOS transistor MN 1  is turned on, the third node n 3  is in the ground state. A large voltage is applied to the third node n 3  instantaneously by a current applied through the second PMOS transistor MP 2 . By the instantaneous large voltage, the voltage of the third node n 3  becomes higher than a voltage by a current signal outputted from the light receiving device PD. At this point, the second switching signal S 2  of the first voltage level L 1  is applied to the second switch SW 2 . The second switch SW 2  is turned-on and the raised voltage of the third node n 3  is discharged to the ground terminal through the third NMOS transistor MN 3 . 
         [0054]    Through a discharging process, the magnitude of a current applied through the second PMOS transistor MP 2  becomes identical to the magnitude of a current signal outputted from the light receiving device PD. At this point, the second switching signal S 2  of the second voltage level L 2  is applied to the second switch SW 2  and the second switch SW 2  is turned-off. 
         [0055]    An ideal light receiving device PD generates only a current signal proportional to the amount of incident light. However, a current signal is generated even when light is not incident due to the thermal cause and insulation defect of the light receiving device PD. This is called dark current. In order for accurate current signal measurement and amplification, the current offset removal unit  230  is required. 
         [0056]    The current offset removal unit  240  includes first to nth current sources CS 1  to CSn and first to nth control switches SW 01  to SW 0   n . The current source is a device applying a constant current regardless of an applied voltage. The first to nth current sources CS 1  to CSn are connected respectively between source terminals and a power terminal VDD of the first to nth control switches SW 01  to SW 0   n . Drain terminals of the first to nth control switches SW 01  to SW 0   n  are connected to the second node n 2  and first to nth control signals S 01  to S 0   n  are applied to gate terminals, respectively. The first to nth control signals S 01  to S 0   n  have a first voltage level L 1  according to a high state and a second voltage level L 2  according to a low state. 
         [0057]    The magnitude of a dark current generated according to the characteristics of a material constituting the light receiving device PD. Accordingly, the first to nth current sources CS 1  to CSn activated in accordance with the magnitude of a predetermined dark current are selected. Control signals of the second voltage level L 2  are applied to gate terminals of first to nth dark current removal switches SW 01  to SW 0   n  connected to the activated first to nth current sources CS 1  to CSn. 
         [0058]    Control signals of the first voltage level L 1  are applied to the gate terminals of the first to nth dark current removal switches SW 01  to SW 0   n  connected to the inactivated first to nth current sources CS 1  to CSn. The activated firsts to nth current sources CS 1  to CSn allow a current having a magnitude identical or similar to the magnitude of a dark current to flow. Accordingly, a current corresponding to a dark current is not applied to the current signal amplification unit  250 . 
         [0059]    The current signal amplification unit  250  amplifies the magnitude of a current signal generated from the light receiving device PD. The current signal amplification unit  250  includes second and third PMOS transistor MP 2  and MP 3 , first to nth current signal amplification transistors MB 1  to MBn, and first to nth amplification switches SWB 1  to SWBn. A source terminal of the second PMOS transistor MP 2  is connected to the power terminal VDD. A drain terminal and a gate terminal of the second PMOS transistor MP 2  are connected to the second node n 2 . 
         [0060]    A source terminal of the third PMOS transistor MP 3  is connected to the power terminal VDD and its drain terminal is connected to a fourth node n 4 . A gate terminal of the third PMOS transistor MP 3  is connected to the second node n 2 . Accordingly, a gate terminal of the third PMOS transistor MP 3  is connected to the drain terminal of the second PMOS transistor MP 2 . 
         [0061]    Source terminals of first to nth current signal amplification transistors MB 1  to MBn are connected to the power terminal VDD and their gate terminals are connected to the second node n 2 . Drain terminals of first to nth current signal amplification transistors MB 1  to MBn are connected to source terminals of the first to nth amplification switches SWB 1  to SWBn, respectively. Drain terminals of the first to nth amplification switches SWB 1  to SWBn are connected to the fourth node n 4  and first to nth amplification signals SB 1  to SBn are applied to gate terminals of the first to nth amplification switches SWB 1  to SWBn. The first to nth amplification signals SB 1  to SBn have a first voltage level L 1  according to a high state and a second voltage level L 2  according to a low state. 
         [0062]    An output terminal OUT is connected to the fourth node n 4 . A current signal amplified through the first to nth current signal amplification transistors MB 1  to MBn is outputted to the output terminal OUT through the fourth node n 4 . 
         [0063]    Since the gate terminals of the first to nth current signal amplification transistors MB 1  to MBn and the second and third PMOS transistors MP 2  and MP 3  are all connected to the second node n 2 , an applied gate signal is identical. Accordingly, the magnitude of a current flowing in the first to nth current signal amplification transistors MB 1  to MBn and the third PMOS transistors MP 3  is identical to the magnitude of a current flowing in the second PMOS transistor MP 2 . The magnitude of a current flowing in the second PMOS transistor MP 2  is identical to the magnitude of a current signal outputted from the light receiving device PD. Therefore, a current having the same magnitude as a current signal outputted from the light receiving device PD is applied to the first to nth current signal amplification transistors MB 1  to MBn. According to the number of the activated first to nth current signal amplification transistors MB 1  to MBn, the amplification of a current signal is adjusted. 
         [0064]    As one example, in order to amplify a current signal 50 times, first to fiftieth amplification signals SB 1  to SB 50  of the second voltage level L 2  are applied to the gate terminals of first to fiftieth amplification switches SWB 1  to SWB 50  connected to first to fiftieth current signal amplification transistors MB 1  to MB 50 . A current having the same magnitude as a current signal outputted from the light receiving device PD is applied to the fourth node n 4  through the first to fiftieth transistors MB 1  to MB 50 . Accordingly, the 50 times amplified current signal is outputted through the output terminal OUT connected to the fourth node n 4 . 
         [0065]    As one example, the cross-sectional areas of the first to nth current signal amplification transistors MB 1  to MBn may be different from that of the second PMOS transistor MP 2 . As one example, when the ratios of the cross-sectional areas of the first to nth current signal amplification transistors MB 1  to MBn are increased, the number of transistors in the current signal amplification unit  250  may be reduced. 
         [0066]    The current-voltage selection unit  260  converts an amplified current signal into a voltage signal. The current-voltage selection unit  260  includes a third switch SW 3  and a resistor R. A drain terminal of the third switch SW 3  is connected to the fourth node n 4  and its source terminal is connected to the resistor R. A third switching signal S 3  is applied to a gate terminal of the third switch SW 3 . The third switching signal S 3  has a first voltage level L 1  according to a high state and a second voltage level L 2  according to a low state. The resistor R is connected between a source terminal of the third switch SW 3  and the ground terminal. 
         [0067]    In the case of a current signal out mode, a third switching signal S 3  of the second voltage level L 2  is applied to the gate terminal of the third switch SW 3 . The third switch SW 3  is turned-off and an amplified current signal is outputted to the output terminal OUT through the fourth node n 4 . 
         [0068]    In the case of a voltage signal out mode, the third switching signal S 3  of the second voltage level L 1  is applied to the gate terminal of the third switch SW 3 . The third switch SW 3  is turned-off and an amplified current signal is applied to the resistor R through the fourth node n 4 . The amplified current signal is converted into a first voltage signal by the resistor R. The first signal is outputted again to the output terminal OUT through the fourth node n 4 . 
         [0069]    The multiplier  200  amplifies a current signal outputted from the light receiving device PD. The multiplier  200  removes a dark current generated from the light receiving device PD by the current offset removal unit  240  so as to improve output efficiency. Additionally, the current-voltage selection unit  260  converts an amplified current signal into a first voltage signal. By outputting an amplified current signal or converting an amplified current signal into a first voltage signal and outputting it, selective output is possible. 
         [0070]      FIG. 3  is a circuit diagram illustrating the multi input amplifier shown in  FIG. 1  according to an embodiment of the present invention. Referring to  FIG. 3 , the multi input amplifier unit  300  is identical to the first to nth multi input amplifiers AMP 1  to AMPn shown in  FIG. 1 . The multi input amplifier  300  includes a first amplifier unit  310 , a differential amplifier  320 , a first output unit  330 , a second amplifier unit  340 , and a second output unit  350 . 
         [0071]    The first amplifier unit  310  includes a first reset switch SWI 1 , first to seventh switches SW 1  to SW 7 , and first and second capacitors C 1  and C 2 . One end of the first reset switch SWI 1  is connected to a first node n 1  and the other end is connected to a common terminal VCM. An input terminal IN is connected to a first node n 1  and a current signal or a first voltage signal is applied to the node n 1 . 
         [0072]    The first switch SW 1  may be connected to between the first and second nodes n 1  and n 2 . One end of the second switch SW 2  is connected to an offset terminal OFFSET and the other end is connected to a third node n 3 . The third switch SW 3  may be connected to between the second and third nodes n 2  and n 3 . The first capacitor C 1  may be connected to between the second and fourth nodes n 2  and n 4 . The second capacitor C 2  may be connected to between the third and fifth nodes n 3  and n 5 . 
         [0073]    One end of the fourth switch SW 4  is connected to the fourth node n 4  and the other end is connected to the common terminal VCM. One end of the fifth switch SW 5  is connected to the common terminal VCM and the other end is connected to the fifth node n 5 . One end of the sixth switch SW 6  is connected to the fourth node n 4  and the other end is connected to the fifth node n 5 . The other ends of the sixth and seventh switches SW 6  and SW 7  are connected to the differential amplifier  320 . 
         [0074]    The first output  330  includes a third capacitor C 3  and eighth and ninth switches SW 8  and SW 9 . One end of the eighth switch SW 8  is connected to a sixth node n 6  and other end is connected to the common terminal VCM. One end of the ninth switch SW 9  is connected to the other end of the sixth switch SW 6  and the other end of the ninth switch SW 9  is connected to the common terminal VCM. The third capacitor C 3  is connected to the sixth node n 6 . One end of the ninth switch SW 9  is connected to the sixth node n 6  and other end is connected to the common terminal VCM. A first output terminal OUT 1  is connected to the sixth node n 6 . 
         [0075]    The second amplifier unit  340  includes a second reset switch SWI 2 , tenth to 16th switches SW 10  to SW 16 , and fourth and fifth capacitors C 4  and C 5 . One end of the second reset switch SWI 2  is connected to the seventh node n 7  and the other end is connected to the common terminal VCM. The common terminal VCM is connected to the seventh node n 7 . The tenth switch SW 10  is connected to between the seventh and eighth n 7  and n 8 . One end of the 11th switch SW 11  is connected to the input terminal IN and the other end is connected to the ninth node n 9 . The 12 th switch SW 12  is connected between the eighth and ninth nodes n 8  and n 9 . 
         [0076]    The fourth capacitor C 4  is connected between the eighth and tenth nodes n 8  and n 10  and the fifth capacitor C 5  is connected between the ninth and 11th nodes n 9  and n 11 . One end of the 13th switch SW 13  is connected to the tenth node n 10  and the other end is connected to the common terminal VCM. One end of the 14th switch SW 14  is connected to the common terminal VCM and the other end is connected to the 11th node n 11 . One end of the 15th switch SW 15  is connected to the tenth node n 10  and one end of the 16th switch SW 16  is connected to the 11th node n 11 . The other ends of the 15th and 16th switches are connected to the differential amplifier  320 . 
         [0077]    The second amplifier unit  350  includes a sixth capacitor C 6  and 17th and 18th switches SW 17  and SW 18 . One end of the 17th switch SW 17  is connected to the 12th node and the other end is connected to the common terminal VCM. One end of the 18th switch SW 18  is connected to the other end of the 15th switch SW 15 . The other end of the 18th switch SW 18  is connected to the common terminal VCM. The sixth capacitor C 6  is connected to the 12th node n 12 . 
         [0078]    According to the present invention, a common mode voltage is applied through the command terminal VCM. According to the present invention, the first to 18th switches SW 1  to SW 18  and the first and second reset switches SWI 1  and SWI 2  may be transistors. 
         [0079]      FIG. 4  is a signal diagram illustrating clock signals inputted to the multi input amplifier shown in  FIG. 3  according to an embodiment of the present invention. Referring to  FIGS. 3 and 4 , the first to 18th switches SW 1  to SW 18  and the first and second reset switches SWI 1  and SWI 2  in the multi input amplifier  300  of  FIG. 3  are turned-on or turned-off by a clock signal of  FIG. 4 . The multi input amplifier  300  has a structure that is symmetric on the basis of a first output terminal OUT 1  and a second output terminal OUT 2 . Accordingly, the same clock signal is applied to switches at the symmetric positions. The drive of the multi input amplifier  300  may be largely divided into a sampling mode and an amplification mode and may then be described. 
         [0080]    In more detail, referring to  FIGS. 3 and 4 , first and second reset signals IRST 1  and IRST 2  are applied to the gate terminals of the first and second reset terminals SWI 1  and SWI 2 . A first initial value sampling signal QR 1  is applied to the gate terminals of the first and tenth switches SW 1  and SW 10  and a second initial sampling signal QR 2  is applied to the gate terminals of the fourth and 13th switches SW 4  and SW 13 . A first data sampling signal QD 1  is applied to the gate terminals of the second and 11th switches SW 2  and SW 11  and a second data sampling signal QD 2  is applied to the gate terminals of the fifth and 14th switches SW 5  and SW 14 . A first sampling mode signal Q 1  is applied to the gate terminals of the ninth and 18th switches SW 9  and SW 18  and a second sampling mode signal Q 2  is applied to the gate terminals of the eighth and 17th switches SW 8  and SW 17 . 
         [0081]    An amplification mode signal Q 3  is applied to the gate terminals of the third, sixth, seventh, 12th, 15th, and 16th switches SW 3 , SW 6 , SW 7 , SW 12 , SW 15 , and SW 16 . The first and second reset signals IRST 1  and IRST 2 , the first and second initial value sampling signals QR 1  and QR 2 , the first and second data sampling signals QD 1  and QD 2 , the first and second sampling mode signals Q 1  and Q 2 , and the amplification mode signal Q 3  have a first voltage level L 1  according to a high level and a second voltage level L 2  according to a low state. 
         [0082]    A current signal or a first voltage signal amplified from the multiplier  200  (see  FIG. 2 ) is applied to the input terminal IN. Once the first voltage signal is applied to the input terminal IN, a first reset signal IRST 1  is applied to the gate terminals of the first and second reset switches SWI 1  and SWI 2 . The first reset signal IRST 1  has the second voltage level L 2  at all times. Once an amplified current signal is applied to the input terminal IN, the second reset signal IRST 2  is applied to the gate terminals of the first and second reset switches SWI 1  and SWI 2 . 
         [0083]    Once an amplified current signal is applied to the input terminal IN, at the initial time t 0 , the amplification mode signal Q 3  of the second voltage level L 2  is applied to the gate terminals of the third, sixth, and seventh switches SW 3 , SW 6 , and SW 7 . Accordingly, the third, sixth, and seventh switches SW 3 , SW 6 , and SW 7  are turned-off. 
         [0084]    At the first time t 1 , the second reset signal IRST 2  of the first voltage level L 1  is applied to the gate terminal of the first reset switch SWI 1 . The first initial value sampling signal QR 1  of the first voltage level L 1  is applied to the gate terminal of the first switch SW 1  and the second initial value sampling signal QR 2  is applied to the gate terminal of the fourth switch SW 4 . Accordingly, the first reset switch SWI 1  and the first and fourth switches SW 1  and SW 4  are turned-on at the same time. As the first reset switch SWI 1  is turned-on, a common mode voltage may be applied to the first node n 1 . An amplified current signal applied through the input terminal IN may have an initial voltage as a common mode voltage. 
         [0085]    At the second time t 2 , the second reset signal IRST 2  of the second voltage level L 2  is applied to the gate terminal of the first reset switch SWI 1 . As the first switch SW 1  is turned-on, the voltage of the second node n 2  rises in proportion to an input of a current signal amplified based on a common mode voltage. When the voltage of the second node n 2  rises, the amount of electric charges charged to the first capacitor C 1  is increased. As the fourth switch SW 4  is turned-on, a common mode voltage is applied to the fourth node n 4 . 
         [0086]    At the third time t 3 , the first initial value sampling signal QR 1  of the second voltage level L 2  is applied to the gate terminal of the first switch SW 1 . Accordingly, the first switch SW 1  is turned-off and charging the first capacitor C 1  stops. 
         [0087]    The second initial value sampling signal QR 2  applied to the fourth switch SW 4  shifts into the second voltage level L 2  before the third time t 3 . When the first switch SW 1  is turned-off, electric charges remaining in a channel area of the first switch SW 1  may affect the first capacitor C 1 . An amplified current signal and a first voltage signal applied to the input terminal IN may vary according to the magnitude of a current signal generated by the light receiving device PD of the multiplier  200  and the amplification degree of the current signal amplifier unit  250 . Since a voltage applied to the first switch SW 1  is not constant, this affects the first capacitor C 1  differently. 
         [0088]    Since a common mode voltage is applied to the fourth node n 4  at all times, this affects the first capacitor C 1  constantly. Accordingly, when the fourth switch SW 4  is turned-off first, the fourth node n 4  becomes in a floating state. When the first switch SW 1  is turned-off after a predetermined time, due to electric charges remaining in a channel area of the first switch SW 1 , the voltage of the second node n 2  rises and also the voltage of the fourth node n 4  rises at the same time. Since the voltages of the second and fourth nodes n 2  and n 4  rise at the same time, the amount of electric charges charged in the first capacitor C 1  does not change. 
         [0089]    At the first time t 1 , the first and second sampling mode signals Q 1  and Q 2  of the first voltage level L 1  are generated. The ninth switch SW 9  is turned-on by the first sampling mode signal Q 1  of the first voltage level L 1  and the eighth switch SW 8  is turned-on by the second sampling mode signal Q 2 . Since a common mode voltage is applied to the both ends of the third capacitor C 3 , the third capacitor C 3  is not charged. According to the present invention, a sampling mode starts at the first time t 1 . 
         [0090]    At the fourth time t 4 , the first and second sampling signals QD 1  and QD 2  of the first voltage level L 1  are generated. The second switch SW 2  is turned-on by the first data sampling signal QD 1  of the first voltage level L 1  and the fifth switch SW 5  is turned-on by the second data sampling signal QD 2 . An offset voltage is applied to the third node n 3  through the second switch SW 2 . A common mode voltage is applied through the fifth switch SW 5 . Accordingly, the amount of electric charges proportional to a difference between an offset voltage and a common mode voltage is charged to the second capacitor C 2  disposed between the third node n 3  and the fifth node n 5 . 
         [0091]    At the sixth time t 6 , the first data sampling signal QD 1  shifts into the second voltage level L 2 . The second data sampling signal QD 2  shifts into the second voltage level L 2  before the sixth time t 6 . Accordingly, after the fifth switch SW 5  is turned-off, the second switch SW 2  is turned-off. This is the same reason that the after the fourth switch SW 4  is turned-off, the first switch SW 1  is turned-off. 
         [0092]    At the sixth time t 6 , the first sampling mode signal Q 1  shifts into the second voltage level L 2 . The second sampling mode signal Q 2  shifts into the second voltage level L 2  before the sixth time t 6 . Accordingly, after the eighth switch SW 8  is turned-off, the ninth switch SW 9  is turned-off. This is the same reason that the after the fourth switch SW 4  is turned-off, the first switch SW 1  is turned-off. According, at the sixth time t 6 , the sampling mode of a signal is terminated. 
         [0093]    At the seventh time t 7 , the amplification mode signal Q 3  of the first voltage level L 1  is generated. Accordingly, the third, sixth, and seventh switches SW 3 , SW 6 , and SW 7  are turned-on by the amplification mode signal Q 3  of the first voltage level L 1 . The first sampling voltage generated by the amount of electric charges stored in the first capacitor C 1  is applied to the differential amplifier  320  and the third capacitor C 3  through the sixth switch SW 6 . The second sampling voltage generated by the amount of electric charges stored in the second capacitor C 2  is applied to the differential amplifier  320  and the third capacitor C 3  through the seventh switch SW 7 . The first and second sampling voltages are outputted to the sixth node n 6  through the differential amplifier  320 . According to the present invention, a time of the amplification mode signal Q 3  of the first voltage level L 1  is defined as an amplification mode. 
         [0094]    The gain of a first output voltage outputted to the first output terminal OUT 1  is determined by a ratio of the capacity of the third capacitor C 3  to the sum of the capacities of the first and second capacitors C 1  and C 2 . In more detail, if the sum of the capacities of the first and second capacitors C 1  and C 2  is identical to the capacity of the third capacitor D 3 , the first and second sampling voltages are outputted as a first output voltage to the first output terminal OUT 1 . If the capacity of the first capacitor C 1  is two times the capacity of the third capacitor C 3 , twice the first and second sampling voltages are outputted as a first output voltage to the first output terminal OUT 1 . 
         [0095]    At the eighth time t 8 , the amplification mode signal Q 3  shifts into the second voltage level L 2 . The third, sixth, and seventh switches SW 3 , SW 6 , and SW 7  are turned-off and the amplification mode is terminated. 
         [0096]    The second amplifier unit  340  and the second output unit  350  have symmetric structures to the first input unit  320  and the first output unit  330 , respectively. At the initial time t 0 , the amplification mode signal Q 3  of the second signal level L 2  is applied to the 12th, 16th, and 17th switches SW 12 , SW 16 , and SW 17 . Accordingly, the 12th, 16th, and 17th switches SW 12 , SW 16 , and SW 17  are turned-off. 
         [0097]    At the first time t 1 , the second reset signal IRST 2  of the first voltage level L 1  is applied to the second reset switch SWI 2 . A common mode voltage is applied to the seventh node n 7  through the second reset switch SWI 2 . Since a common mode voltage is applied to the seventh node n 7 , it is unnecessary to apply a common mode voltage through the second reset switch SWI 2 . However, in order for a symmetric structure of the multi input amplifier  300 , the second reset switch SWI 2  exists. 
         [0098]    At the second time t 2 , the second reset signal IRST 2  of the second voltage level L 2  is applied to the second reset switch SWI 2 . Accordingly, the second reset switch SWI 2  is turned-off. 
         [0099]    At the first time t 1 , the first and second initial sampling signals QR 1  and QR 2  of the first voltage level L 1  are generated. The tenth switch SW 10  is turned-on by the first initial sampling signal QR 1  of the first voltage level L 1 . The 13th switch SW 13  is turned-on by the second initial sampling signal QR 2  of the first voltage level L 1 . A common mode voltage is applied to the eighth node n 8  through the tenth switch SW 10 . A common mode voltage is applied to the tenth node n 10  through the 13th switch SW 10 . The fourth capacitor C 4  is connected to between the eighth node n 8  and the tenth node n 10 . Since a common mode voltage is applied to the both ends of the fourth capacitor C 4 , electric charges are not charged to the fourth capacitor C 4 . 
         [0100]    At the third time t 3 , the first initial value sampling signal QR 1  of the second voltage level L 2  is applied to the tenth switch SW 10 . The second initial value sampling signal QR 2  of the second voltage level L 2  is applied to the 13th switch SW 13  before the third time t 3 . Accordingly, after the 13th switch SW 13  is turned-off, the tenth switch SW 10  is turned-off. This is not to affect the amount of electric charges charged to the fourth capacitor C 4 . 
         [0101]    Additionally, at the first time t 1 , the first and second sampling mode signals Q 1  and Q 2  of the first voltage level L 1  are generated. The second sampling mode signal Q 2  of the first voltage level L 1  is applied to the gate terminal of the 17th switch SW 17 . The 17th and 18th switches SW 17  and SW 18  are turned-on and a common mode voltage is applied. Since the voltages at both ends are the same, electric charges are not charged to the sixth capacitor C 6  connected between the 17th and 18th switches SW 17  and SW 18 . At the first time t 1 , a sampling mode starts. 
         [0102]    At the fourth time t 4 , the second reset signal IRST 2  of the first voltage level L 1  is applied to the first reset switch SWI 1 . Accordingly, the first reset switch SWI 1  is turned-off. The first data sampling signal QD 1  of the first voltage level L 1  is applied to the 11th switch SW 11 . The second data sampling signal QD 2  of the first voltage level L 1  is applied to the 14th switch SW 14 . The 11th and 14th switches SW 11  and SW 14  are turned-on. Once the first reset switch SWI 1  is turned-on, an amplified current signal applied through the input terminal IN may have an initial voltage as a common mode voltage. 
         [0103]    At the fifth time t 5 , the second reset signal IRST 2  of the second voltage level L 2  is applied to the first reset switch SWI 1 . The first reset switch SWI 1  is turned-off. 
         [0104]    An amplified current signal is applied to the ninth node n 9  through the 11th switch SW 11  and the voltage of the ninth node n 9  is increased more than a common mode voltage. A common mode voltage is applied to the 11th node n 11  through the 14th switch SW 14 . The fifth capacitor C 5  is connected between the ninth node n 9  and the 11th node n 11 . Accordingly, the amount of electric charges of the fifth capacitor C 5  is charged by the increased voltage of the ninth node n 9 . 
         [0105]    At the sixth time t 6 , the first data sampling signal QD 1  shifts into the second voltage level L 2 . The second data sampling signal QD 2  shifts into the second voltage level L 2  before the sixth time t 6 . When the 14th switch SW 14  is turned-off, the 11th switch SW 11  is turned-off sequentially. This is not to affect the amount of electric charges charged to the fifth capacitor C 5 . 
         [0106]    At the sixth time t 6 , the first sampling mode signal Q 1  shifts into the second voltage level L 2 . The second sampling mode signal Q 2  shifts into the second voltage level L 2  before the sixth time t 6 . When the 17th switch SW 17  is turned-off, the 18th switch SW 11  is turned-off sequentially. This is not to affect the amount of electric charges charged to the sixth capacitor C 6 . At the sixth time t 6 , the sampling mode is terminated. 
         [0107]    At the seventh time t 7 , the amplification mode signal Q 3  of the first voltage level L 1  is generated. The amplification mode signal Q 3  of the first voltage level L 1  is applied to the 12th, 15th, and 16th switches SW 12 , SW 15 , and SW 16 . Accordingly, the 12th, 15th, and 16th switches SW 12 , SW 15 , and SW 16  are turned-on. At the seventh time t 7 , an amplification mode starts. 
         [0108]    The fifth sampling voltage generated by the amount of electric charges charged to the fifth capacitor C 5  is applied to the differential amplifier  320  and the sixth capacitor C 6  through the 16th switch SW 16 . The fifth sampling voltage is outputted to the 12th node n 12  through the differential amplifier  320 . The gain of a second output voltage outputted through the second output terminal OUT 2  is determined by a ratio of the capacity of the sixth capacitor C 6  to the sum of the capacities of the fourth and fifth capacitors C 4  and C 5 . 
         [0109]    At the eighth time t 8 , the amplification mode signal Q 3  shifts into the second voltage level L 2 . The 12th, 15th, and 16th switches SW 12 , SW 15 , and SW 16  are turned-off and the amplification mode is terminated. 
         [0110]    When an amplified current signal is applied to the input terminal IN of the multi input amplifier  300 , a charging time of the first and fifth capacitors C 1  and C 5  charged by the amplified current signal may be adjusted. Through a charging time adjustment, the magnitudes of the first and fifth sampling voltages are changed. Accordingly, an output gain may be adjusted. By adjusting an applying time of the first initial value sampling signal QR 1  and the first data sampling signal QD 1 , a charging time adjustment is possible. 
         [0111]    According to an embodiment of the present invention, a current-voltage conversion amplifier circuit may select a voltage and current mode in order for amplification. In the case of a current mode, by adjusting a sampling time of a multi input amplifier, a desired output voltage may be obtained. 
         [0112]    In describing each drawing, like reference numerals refer to like elements. In the accompanying drawings, the dimensions of structures are exaggerated for clarity of illustration. It will be understood that the terms “first” and “second” are used herein to describe various components but these components should not be limited by these terms. These terms are used only to distinguish one component from other components. For example, a first component may be referred to as a second component and vice versa without departing from the scope of the present invention. The terms of a singular form may include plural forms unless they have a clearly different meaning in the context. 
         [0113]    As mentioned above, embodiments are disclosed in the drawings and the specification. Although specific terms are used herein, this is just to describe the present invention and does not limit the meaning or the scope of the present invention listed in claims. Therefore, it is apparent to those skilled in the art that various embodiments and equivalent other embodiments are possible. Hence, the real protective scope of the present invention shall be determined by the technical scope of the accompanying claims.

Technology Category: h