Abstract:
A sense amplifier resistant to malfunctions associated with offsets in inverter pairs is presented. The sense amplifier includes inverter pairs and a controller. Any one input terminal of the inverter pairs is electrically connected to a bit line and the other one input terminal is electrically connected to a /bit line. The controller is configured to precharge the bit line and the /bit line to a level corresponding to an offset of the inverter pairs in response to a first control signal. The controller senses a voltage difference of the bit line and the /bit line using the inverter pairs by connecting output terminals of the inverter pairs to the bit line pairs in response to a second control signal.

Description:
CROSS-REFERENCES TO RELATED PATENT APPLICATION 
     The present application claims priority under 35 U.S.C 119(a) to Korean Application No. 10-2009-0058933, filed on Jun. 30, 2009, in the Korean Intellectual Property Office, which is incorporated herein by reference in its entirety as set forth in full. 
     BACKGROUND 
     1. Technical Field 
     Embodiments of the present invention described herein relate to a semiconductor circuit technology, and in particular, to a sense amplifier and a semiconductor integrated circuit using the same. 
     2. Related Art 
     A semiconductor integrated circuit  10  according to the conventional art includes a bit line ‘BL’, a /bit line ‘BLB’, a word line ‘WL’, a memory cell  11 , a sense amplifier  12 , and precharge circuits  13  and  14 , as shown in  FIG. 1 . 
     The sense amplifier  12 , which is a component for sensing and amplifying data recorded in the memory cell  11 , is electrically connected between the bit line ‘BL’ and the /bit line ‘BLB’ and includes a plurality of transistors ‘M 1  to M 6 ’. 
     The sense amplifier  12 , which is in a cross coupled latch form, includes inverter pairs that are configured of transistors M 1  and M 2  and transistors M 3  and M 4 . 
     The transistor ‘M 5 ’ is electrically connected between the cross coupled latch and a power supply terminal ‘VCORE’. A gate of the transistor ‘M 5 ’ receives a control signal ‘SAP’. The transistor ‘M 6 ’ is electrically connected between the cross coupled latch and a ground terminal ‘VSS’. A gate of the transistor ‘M 6 ’ receives a control signal ‘SAN’. The control signals ‘SAP and SAN’ are signals that determine a timing supplying power to the sense amplifier  12 . 
     The precharge circuits  13  and  14  precharge the bit line pairs to a bit line precharge voltage ‘VBLP’ level according to a bit line equalize signal ‘BLEQ’. The precharge circuits  13  and  14  may be configured of a plurality of transistors ‘M 7  to M 12 ’. 
     At this time, a mismatch between the transistors that configure the inverter pairs of the sense amplifier  12  may occur due to a problem of the elements or processes. An offset between the transistors forming the inverter pair, that is, a difference in a threshold voltage that is different from a circuit design may occur due to the mismatch. 
     In addition, since the transistors ‘M 5  and M 6 ’ and the transistors ‘M 7  to M 12 ’ configuring the precharge circuits  13  and  14  are a component that has a connection with a power supply, they are designed at a larger size than the transistors ‘M 1  to M 4 ’ configuring the inverter pairs of the sense amplifier  12 . 
     The semiconductor integrated circuit according to the conventional art, which is configured as described above, precharges the bit line ‘BL’ and the /bit line ‘BLB’ at the bit line precharge voltage ‘VBLP’ level by the precharge circuits  13  and  14  before the word line ‘WL’ is activated. 
     Thereafter, as the word line ‘WL’ is activated for read or refresh operations, the charge sharing of the bit line ‘BL’ and the /bit line ‘BLB’ is made. 
     After a time elapses by a degree that the voltage difference of the bit line ‘BL’ and the /bit line ‘BLB’ is the desired level or more by the charge sharing, the control signals ‘SAP and SAN’ are activated. 
     The sense amplifier  12  is operated according to the activation of the control signals SAP and SAN, such that the sensing and amplifying operations of data recorded in the memory cell  1  can be made. 
     The semiconductor integrated circuit according to the above-mentioned conventional art has the following problems. 
     First, the bit line ‘BL’ and the /bit line ‘BLB’ are precharged at the same voltage level, that is, the bit line precharge voltage ‘VBLP’ level. However, the sense amplifier does not reflect the voltage difference of the bit line ‘BL’ and the /bit line ‘BLB’ due to the offset of the inverter pairs and thus, a malfunction may occur. 
     For example, it is assumed that “1” is recorded in the memory cell  11 . When the word line ‘WL’ is activated, the voltage level of the bit line ‘BL’ is higher than the bit line precharge voltage ‘VBLP’ and the voltage level of the /bit line ‘BLB’ will maintain the bit line precharge voltage ‘VBLP’. At this time, if it is assumed that the threshold voltage of the transistor ‘M 2 ’ is in a lower state than that of the design and the threshold voltage of the transistor ‘M 4 ’ is in a higher state than that of the design, the voltage of the bit line ‘BL’ is discharged through the transistor ‘M 6 ’ by the transistor ‘M 2 ’ such that the data of the memory cell  11  is wrongly sensed as “0”. 
     Second, since the transistors ‘M 5  and M 6 ’ for supplying power and the transistors ‘M 7  to M 12 ’ for the precharge operation are needed, the reduction in the circuit area to form the transistors occurs. 
     SUMMARY 
     In one embodiment of the present invention a sense amplifier includes: inverter pairs of which any one input terminal is electrically connected to a bit line and the other input terminal is electrically connected to a /bit line; and a controller configured to precharge the bit line and the /bit line to a level corresponding to an offset of the inverter pairs in response to a first control signal and to sense a voltage difference of the bit line and the /bit line by the inverter pairs by electrically connecting output terminals of the inverter pairs to the bit line pairs in response to a second control signal. 
     In another embodiment of the present invention, a sense amplifier includes: a first inverter and a second inverter that are electrically connected between a bit line and a /bit line and forms a cross coupled latch; a first transistor that is configured to connect an input terminal of the first inverter to an output terminal thereof in response to a first control signal; a second transistor that is configured to connect an input terminal of the second inverter to an output terminal thereof in response to the first control signal; a third transistor that is configured to connect the output terminal of the first inverter to the /bit line in response to a second control signal; and a fourth transistor that is configured to connect the output terminal of the second inverter to the bit line in response to the second control signal. 
     In still another embodiment of the present invention, a semiconductor integrated circuit includes: a memory cell; bit line pairs configured of a bit line and a /bit line that are connected to input and output data to the memory cell; and an amplifying sensor configured to include inverter pairs connected between the bit line pairs, precharge the bit line and the /bit line to a level corresponding to an offset voltage of the inverter pairs in response to a first control signal, and sense a voltage difference of the bit line and the /bit line by the inverter pairs by connecting the output terminals of the inverter pairs to the bit line pairs in response to the second control signal. 
     These and other features, aspects, and embodiments are described below in the section “Detailed Description.” 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, aspects, and embodiments are described in conjunction with the attached drawings, in which: 
         FIG. 1  is a circuit diagram of a semiconductor integrated circuit according to the conventional art; and 
         FIG. 2  is a circuit diagram of a semiconductor integrated circuit according to the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, preferred embodiments will be described in more detail with reference to the accompanying drawings. 
       FIG. 2  is a circuit diagram of a semiconductor integrated circuit according to the embodiment. 
     As shown in  FIG. 2 , a semiconductor integrated circuit  100  according to the present invention includes bit line pairs that are configured of a bit line ‘BL’ and a /bit line ‘BLB’, a memory cell  11 , and a sense amplifier  110 . 
     The sense amplifier  110  is electrically connected between the bit line ‘BL’ and the /bit line ‘BLB’ and is applied with a power supply voltage ‘VCORE’ and a ground voltage ‘VSS’. 
     The sense amplifier  110  commonly uses the power supply voltage ‘VCORE’ for precharging the bit line pairs and sensing the voltage difference of the bit line pairs (sense data recorded in the memory cell). 
     The sense amplifier  110  includes a first inverter  111 , a second inverter  112 , and a controller  113 . 
     The first inverter  111  includes fifth and sixth transistors ‘M 21  and M 22 ’. The source of the fifth transistor ‘M 21 ’ is applied with the power supply voltage ‘VCORE’ and the drain of the sixth transistor ‘M 22 ’ is applied with the ground voltage ‘VSS’. 
     The second inverter  112  includes seventh and eighth transistors ‘M 23  and M 24 ’. The source of the seventh transistor ‘M 23 ’ is applied with the power supply voltage ‘VCORE’ and the drain of the eighth transistor ‘M 24 ’ is applied with the ground voltage ‘VSS’. 
     The fifth to eighth transistors ‘M 21  to M 24 ’ of the first and second inverters  111 ,  112  form a structure of a cross coupled latch. 
     The controller  113  is configured to precharge the bit line ‘BL’ and the /bit line ‘BLB’ to a level corresponding to an offset of the inverter pairs  111  and  112  in response to a first control signal ‘S 1 ’ and sense a voltage difference of the bit line ‘BL’ and the /bit line ‘BLB’ using the inverter pairs  111  and  112  by connecting output terminals of the inverter pairs  111  and  112  to the bit line pairs ‘BL and BLB’ in response to a second control signal ‘S 2 ’. 
     The first control signal ‘S 1 ’ is a pulse signal that is generated prior to a setting time from activation timing of a word line driving signal, that is, a signal for activating the word line. It is possible to use a bit line equalize signal as the first control signal ‘S 1 ’. 
     The second control signal ‘S 2 ’ is a signal that delays the word line driving signal by a predetermined setting time. It is possible to use the word line driving signal as the second control signal ‘S 2 ’. 
     The controller  113  includes fifth to eighth transistors ‘M 25  to M 28 ’. 
     The first transistor ‘M 25 ’ is configured to connect the input terminal and output terminal of the first inverter  111  in response to the first control signal ‘S 1 ’. 
     The second transistor ‘M 26 ’ is configured to connect the input terminal and output terminal of the second inverter  112  in response to the first control signal ‘S 1 ’. 
     The third transistor ‘M 27 ’ is configured to connect the output terminal of the first inverter  111  to the bit line ‘BL’ in response to the second control signal ‘S 2 ’. 
     The fourth transistor ‘M 28 ’ is configured to connect the output terminal of the second inverter  112  to the /bit line ‘BLB’ in response to the second control signal ‘S 2 ’. 
     The operation of the semiconductor integrated circuit configured as above according to the present invention will be described below. 
     The first control signal ‘S 1 ’ is generated prior to the activation timing of the word line driving signal. At this time, the second control signal ‘S 2 ’ is in a non-activated state. 
     The first and second transistors ‘M 25  and M 26 ’ are in a turn-on state and the third and fourth transistors ‘M 27  and M 28 ’ are in a turn-off state, during a high level interval of the first control signal ‘S 1 ’. 
     Therefore, the output terminal of the first inverter  111  is electrically separated from the bit line ‘BL’, while the output terminal and input terminal of the first inverter  111  are short from each other and the input terminal of the first inverter  111  is connected to the  /bit line ‘BLB’. Therefore, the offset of the first inverter  111 , that is, the voltage level reflecting the difference between a target threshold voltage and an actual threshold voltage is stored in an effective capacitor of the /bit line ‘BLB’ to precharge the /bit line ‘BLB’. 
     At this time, the effective capacitor does not form an actual circuit configuration, but includes the gate capacitance of all the transistors connected to the /bit line ‘BLB’, etc. 
     Likewise, the output terminal of the second inverter  112  is electrically separated from the /bit line ‘BLB’, while the output terminal and input terminal of the second inverter  112  are short from each other and the input terminal of the second inverter  112  is connected to the bit line ‘BL’. Therefore, the offset of the second inverter  112 , that is, the voltage level reflecting the difference between a target threshold voltage and an actual threshold voltage is stored in an effective capacitor of the bit line ‘BL’ to precharge the bit line ‘BL’. 
     At this time, the precharge voltage level of the bit line ‘BL’ and the precharge voltage level of the /bit line ‘BLB’ have a difference due to the offset of the first inverter  111  and the second inverter  112 . In other words, the bit line ‘BL’ and the /bit line ‘BLB’ are precharged at a level to compensate for the offset in order to prevent malfunction upon sensing the voltage difference of the bit line ‘BL’ and the /bit line ‘BLB’. 
     Thereafter, as the word line ‘WL’ is activated in response to the activation of the word line driving signal, the charge sharing of the bit line ‘BL’ and the /bit line ‘BLB’ is made. 
     After a predetermined time elapses such that the voltage difference of the bit line ‘BL’ and the /bit line ‘BLB’ is the desired level or more by charge sharing, the second control signal ‘S 2 ’ is activated. At this time, the first control signal ‘S 1 ’, which is a pulse form, is in a previously non-activated state prior to the activation timing of the word line driving signal. 
     Therefore, the first and second transistors ‘M 25  and M 26 ’ maintain the turn-off state and the third and fourth transistors ‘M 27  and M 28 ’ are turned-on. 
     As the third and fourth transistors ‘M 27  and M 28 ’ are turned-on, the output terminal of the first inverter  111  is electrically connected to the bit line ‘BL’ and the output terminal of the second inverter  112  is electrically connected to the /bit line ‘BLB’ to perform the operation of sensing data recorded in the memory cell  11 , that is, the operation of sensing the voltage difference of the bit line ‘BL’ and the /bit line ‘BLB’. 
     While certain embodiments have been described above, it will be understood to those skilled in the art that the embodiments described are by way of example only. Accordingly, the apparatus described herein should not be limited based on the described embodiments. Rather, the right scope of the present invention is defined only by the claims. All modifications and changes derived from the meanings, scope, and equivalents of claims should be construed as being included in the scope of the present invention.