Abstract:
A power amplifier includes an inverter amplification section configured to amplify AC components and remove DC components from at least one input signal, an impedance matching section configured to match an impedance of a transmission path of the at least one input signal amplified by the inverter amplification section, and an amplification section configured to amplify an impedance-matched signal from the impedance matching section according to a predetermined gain. The inverter amplification section includes at least one P-channel metal-oxide semiconductor field effect transistor (MOS FET) having a gate configured to receive the at least one input signal and at least one N-channel MOS FET having a gate configured to receive the at least one input signal. The at least one P-channel MOS FET and the at least one N-channel MOS FET are serially connected.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Korean Patent Application No. 2009-0113233 filed on Nov. 23, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to power amplifiers, and more particularly, to a power amplifier that can increase power efficiency by preventing power consumption caused by DC components from an RF input signal. 
     2. Description of the Related Art 
     Mobile communications terminals have been widely used because they are easy to use. As the use of these mobile communications terminals has increased, it has become important to run various kinds of applications to meet consumer demand and allow for long-time use at the same time. 
     In order to extend the use time of a mobile communications terminal, it is important to increase battery capacity. However, the size of batteries is limited since small, lightweight, and thin mobile communications terminals are in demand in the market. Therefore, there is a need to increase the power efficiency of main elements inside a mobile communications terminal. 
     In order to transmit and receive RF signals, this mobile communications terminal uses a power amplifier. This power amplifier takes up a considerable portion of the overall power consumption of the mobile communication terminal. 
     Thus, the power efficiency of the power amplifier needs to be increased. However, as for a power amplifier being used in a mobile communications terminal according to the related art, DC current flows through the power amplifier at all times, which reduces power efficiency. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides a power amplifier that can increase power efficiency by preventing power consumption caused by DC components from an RF input signal. 
     According to an aspect of the present invention, there is provided a power amplifier including: an inverter amplification section configured to amplify AC components and remove DC components from at least one input signal; an impedance matching section configured to match an impedance of a transmission path of the input signal amplified by the inverter amplification section; and an amplification section configured to amplify an impedance-matched signal from the impedance matching section according to a gain set beforehand. The inverter amplification section includes at least one P-channel metal-oxide semiconductor field effect transistor (MOS FET) having a gate configured to receive the at least one input signal and at least one N-channel MOS FET having a gate configured to receive the at least one input signal, where the at least one P-channel MOS FET and the at least one N-channel MOS FET are serially connected. 
     The input signal may include balanced signals including an input signal having a positive level and an input signal having a negative level. 
     The inverter amplification section may include: a first inverter including a first P-channel MOS FET (metal-oxide-semiconductor field-effect transistor) having a drain receiving driving power, a gate receiving the input signal having the positive level, and a source connected to the impedance matching section, and a first N-channel MOS FET having a drain connected to the impedance matching section, connected to the source of the first P-channel MOS FET, a gate receiving the input signal having the positive level, and a source connected to a ground; and a second inverter including a second P-channel MOS FET having a drain being supplied with the driving power, a gate receiving the input signal having the negative level, and a source connected to the impedance matching section, and a second N-channel MOS FET having a drain connected to the impedance matching section, connected to the source of the P-channel MOS FET, a gate receiving the input signal having the negative level, and a source connected to a ground. 
     The impedance matching section may include: a first primary coil having one end receiving operating power and the other end connected to the source of the first P-channel MOS FET and the drain of the first N-channel MOS FET, the first primary coil receiving the amplified input signal having the positive level from the first inverter; a second primary coil having one end receiving the operating power and the other end connected to the source of the second P-channel MOS FET and the drain of the second N-channel MOS FET, the second primary coil receiving the amplified input signal having the negative level from the second inverter; a first secondary coil having one end receiving the operating power and the other end connected to the amplification section, the first secondary coil electromagnetically coupled with the first primary, and receiving the input signal having the positive level from the second primary coil to transmit the received input signal to the amplification section; and a second secondary coil having one end receiving the operating power and the other end connected to the amplification section, the second secondary coil electromagnetically coupled with the second primary coil and receiving the input signal having the positive level from the second primary coil to transmit the received input signal to the amplification section. 
     The amplification section may include a third N-channel MOS FET having a drain being supplied with the driving power, a gate receiving the input signal having the positive level from the other end of the first secondary coil, and a source connected to the ground, the third N-channel MOS FET amplifying the input signal having the positive level from the impedance matching section according to a gain set beforehand to thereby output the amplified input signal having the positive level; and a fourth N-channel MOS FET having a drain being supplied with the driving power, a gate receiving the input signal having the negative level from the other end of the second secondary coil, and a source connected to the ground, the N-channel MOS FET amplifying the input signal having the negative level from the impedance matching section according to a gain set beforehand to thereby output the amplified input signal having the negative level. 
     The power amplifier may further include an intermediate amplification section re-amplifying the input signals amplified by the inverter amplification section according to gains set beforehand, and transmitting the input signals being re-amplified to the impedance matching section. 
     The intermediate amplification section may include a first cascade amplification unit and a second cascade amplification unit each being supplied with the driving power from a driving power terminal, connected in parallel with each other, and receiving the input signal having the positive level and the input signal having the negative level from the inverter amplification section, respectively; and a first cascode amplification unit and a second cascode amplification unit connected in series between the first and second cascade amplification units and a ground terminal, connected in parallel with each other, and receiving the input signal having the positive level and the input signal having the negative level from the inverter amplification section, respectively, the first and second cascade amplification units may include third and fourth P-channel MOS FETs, respectively, while a gate of the third P-channel MOS FET receives the input signal having the positive level or the input signal having the negative level from the inverter amplification section, the gate of the third P-channel MOS FET being connected to that of the fourth P-channel MOS FET, and the first and second cascode amplification units may include third and fourth N-channel MOS FETs, respectively, while a gate of the third N-channel MOS FET receives the input signal having the positive level or the input signal having the negative level from the inverter amplification section, the gate of the fourth N-channel MOS FET being connected in common to that of the fourth N-channel MOS FET. 
     The impedance matching section may include a primary coil having one end electrically connected to a connection terminal between the first cascade amplification unit and the first cascode amplification unit and the other end electrically connected to a connection terminal between the second cascade amplification unit and the second cascode amplification unit, the primary coil receiving the input signal being re-amplified by the intermediate amplification section; and a secondary coil electromagnetically coupled with the primary coil and receiving the input signal being re-amplified from the primary coil. 
     The amplification section may include a third cascode amplification unit and a fourth cascode amplification unit connected in series between the driving power terminal and ground and connected in parallel with each other, the third and fourth cascode amplification units may include fifth and sixth N-channel MOS FETs, respectively, and a gate of the fifth N-channel MOS FET may receive an external gain control signal while a gate of the sixth N-channel MOS FET may receive the input signal having the positive level or the input signal having the negative level from the secondary coil of the impedance matching section. 
     The power amplifier may further include an intermediate amplification section re-amplifying the input signals, amplified by the inverter amplification section, according to gains set beforehand, and transmitting the re-amplified input signals to the impedance matching section. 
     The inverter amplification section may include a first inverter and a second inverter connected in series with each other between a driving power terminal supplying the driving power and ground, the first and second inverters each amplifying the input signal having the positive level according to an inverter method, and a third inverter and a fourth inverter connected in series between the driving power terminal and ground, and amplifying the input signal having the negative level according to an inverter method, the first inverter may include a first P-channel MOS FET having a drain being supplied with the driving power, a gate receiving the input signal having the positive level, and a source connected to the impedance matching section, while the second inverter may include a first N-channel MOS FET having a drain connected to the impedance matching section, connected to the source of the first P-channel MOS FET, a gate receiving the input signal having the positive level, and a source connected to a ground, and the third inverter may include a second P-channel MOS FET having a drain being supplied with the driving power, a gate receiving the input signal having the negative level, and a source connected to the impedance matching section, and the fourth inverter may include a second N-channel MOS FET having a drain connected to the impedance matching section, connected to the source of the second P-channel MOS FET, a gate receiving the input signal having the negative signal, and a source connected to the ground. 
     The intermediate amplification section may include a first cascade amplification unit and a second cascade amplification unit each being supplied with the power terminal from a driving power terminal supplying the driving power, connected in parallel with each other, and receiving the input signal having the positive level and the input signal having the negative level from the inverter amplification section, respectively, and the first and second cascade amplification units may include third and fourth P-channel MOS FETs, respectively, while a gate of the third P-channel MOS FET receives the input signal having the positive level or the input signal having the negative level from the inverter amplification section, the gate of the third P-channel MOS FET being connected in common to that of the fourth N-channel MOS FET, and the first and second cascode amplification units may include third and fourth N-channel MOS FETs, respectively, while a gate of the third N-channel MOS FET receives the input signal having the positive level or the input signal having the negative level from the inverter amplification section, the gate of the third N-channel MOS FET being connected in common to that of the fourth N-channel MOS FET. 
     The impedance matching section may include a primary coil having one end electrically connected to a connection terminal between the first cascade amplification unit and the first cascode amplification unit and the other end electrically connected to a connection terminal between the second cascade amplification unit and the second cascode amplification unit, the primary coil receiving the input signals re-amplified by the intermediate amplification section; and a secondary coil electromagnetically coupled with the primary coil and receiving the input signals being re-amplified from the primary coil. 
     The amplification section may include a third cascode amplification unit and a fourth cascode amplification unit connected in series with the driving power terminal and ground and connected in parallel with each other, the third and fourth cascode amplification units may include fifth and sixth N-channel MOS FETs, respectively, and a gate of the fifth N-channel MOS FET may include an external gain control signal while a gate of the sixth N-channel MOS FET may receive the input signal having the positive level or the input signal having the negative level from the secondary coil of the impedance matching section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic view illustrating the configuration of a power amplifier according to an exemplary embodiment of the present invention; 
         FIG. 2  is a schematic circuit diagram illustrating the power amplifier as shown in  FIG. 1 ; 
         FIG. 3  is a schematic view illustrating the configuration of a power amplifier according to another exemplary embodiment of the present invention; 
         FIG. 4  is a schematic circuit diagram illustrating the power amplifier as shown in  FIG. 3 ; and 
         FIG. 5  is a schematic circuit diagram illustrating a power amplifier according to another exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a schematic view illustrating the configuration of a power amplifier according to an exemplary embodiment of the invention. 
     Referring to  FIG. 1 , a power amplifier  100  according to this embodiment may include an inverter amplification section  110 , an impedance matching section  120 , and an amplification section  130 . 
     The inverter amplification section  110  may amplify an RF input signal according to an inverter method to thereby remove DC components therefrom. 
     The impedance matching section  120  matches the impedance of a transmission path of the RF input signal, amplified by the inverter amplification section  110 , to thereby transmit an impedance-matched signal to the amplification section  130 . 
     The amplification section  130  amplifies the impedance-matched signal from the impedance matching section  120  according to a gain set beforehand to thereby output the impedance-matched signal being amplified. 
       FIG. 2  is a schematic circuit diagram illustrating the power amplifier as shown in  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , the inverter amplification section  110 , which is included in the power amplifier  100  according to this embodiment, may include first and second inverters  111  and  112 . 
     The first inverter  111  may include a first P-channel MOS FET  111   a  and a first N-channel MOS FET  11   b , which are connected in series with each other between a driving power terminal supplying driving power Vdd and a ground. 
     The first P-channel MOS FET  111   a  has a drain being supplied with the driving power Vdd, a gate receiving an input signal RFin+ having a positive level between RF input signals, and a source connected to the first N-channel MOS FET  11   b.    
     The first N-channel MOS FET  11   b  has a drain connected to the source of the first P-channel MOS FET  111   a , a gate receiving the input signal RFin+ having a positive level, and a source connected to a ground. 
     As described above, the first inverter  111  amplifies the input signal RFin+ having a positive level to thereby output an amplified output signal. The amplified output signal is output through a connection terminal between the first P-channel MOS FET  111   a  and the first N-channel MOS FET  11   b . Therefore, the phase of the input signal RFin+ may be shifted such that the output signal has an inverse phase to the phase thereof on the basis of 0V. Therefore, while DC components, included in the input signal RFin+, are removed, AC components can be amplified. 
     Similarly, the second inverter  112  may include a second P-channel MOS FET  112   a  and a second N-channel MOS FET  112   b  that are connected in series between the driving power terminal and ground. Like the configuration of the first inverter  111 , the second P-channel MOS FET  112   a  has a drain being supplied with the driving power Vdd, a gate receiving an input signal RFin− having a negative level between RF input signals, and a source connected to the second N-channel MOS FET  112   b . The second N-channel MOS FET  112   b  has a drain connected to the source of the second P-channel MOS FET  112   a , a gate receiving the input signal RFin− having a negative level, and a source connected to a ground. 
     In the same manner, the second inverter  112  removes DC components, included in the input signal RFin−, and amplifies AC components to thereby transmit an amplified output signal to the impedance matching section  120 . 
     The impedance matching section  120  may include a first primary coil P 1 , a second secondary coil P 2 , a first secondary coil S 1 , and a second secondary coil S 2 . The first primary coil P 1  receives the amplified output signal from the first inverter  111 . The second secondary coil P 2  receives the amplified output signal from the second inverter  112 . The first secondary coil S 1  performs the impedance matching of the amplified output signal according to a turns ratio, determined by electromagnetic coupling between the first primary and secondary coils P 1  and S 1 , to thereby transmit the impedance-matched signal to the amplification section  130 . The second secondary coil S 2  performs the impedance matching of the amplified output signal according to a turns ratio, determined by electromagnetic coupling between the second primary and secondary coils P 2  and S 2  to thereby transmit the impedance-matched signal to the amplification section  130 . 
     One end of the first primary coil P 1  is electrically connected to the second primary coil P 2 , and the other end of the first primary coil P 1  is electrically connected to the connection terminal between the first P-channel MOS FET  111   a  and the first N-channel MOS FET  11   b  of the first inverter  111 , so that the first primary coil P 1  can receive the output signal, obtained by amplifying the input signal RFin+ having a positive level, from the first inverter  111 . 
     One end of the second primary coil P 2  is electrically connected to one end of the first primary coil P 1 , and the other end of the second primary coil P 2  is connected to a connection terminal between the second P-channel MOS FET  112   a  and the second N-channel MOS FET  112   b  of the second inverter  112 , so that the second primary coil P 2  can receive the output signal, obtained by amplifying the input signal RFin− having a negative level, from the second inverter  112 . 
     One end of the first secondary coil S 1  receives operating power Vgate, and the other end thereof is electrically connected to the amplification section  130 , so that the first secondary coil S 1  can transmit the impedance-matched signal to the amplification section  130 . One end of the second secondary coil S 2  receives the operating power Vgate, and the other end thereof is electrically connected to the amplification section  130 , so that the second secondary coil S 2  can transmit the impedance-matched signal to the amplification section  130 . 
     The amplification section  130  may include a third N-channel MOS FET  131  and a fourth N-channel MOS FET  132 . The third and fourth N-channel MOS FETs  131  and  132  are connected in series between the driving power terminal and a ground and are connected in parallel with each other. 
     The third N-channel MOS FET  131  has a drain being supplied with the driving power Vdd, a gate receiving one of the impedance-matched signals, which has a positive level, from the impedance matching section  120 , and a source connected to the ground. 
     The fourth N-channel MOS FET  132  has a drain being supplied with the driving power Vdd, a gate receiving the other one having a negative level from the impedance matching section  120 , and a source connected to the ground. 
     Therefore, the amplification section  130  can amplify the impedance-matched signals with positive and negative levels from the impedance matching section  120 , separately, according to respective gains set beforehand to thereby output amplified signals. 
       FIG. 3  is a schematic view illustrating the configuration of a power amplifier according to another exemplary embodiment of the invention. 
     Referring to  FIG. 3 , a power amplifier  200  according to this embodiment may include an inverter amplification section  210 , an intermediate amplification section  220 , an impedance matching section  230 , and an amplification section  240 . 
     The intermediate amplification section  220  may re-amplify signals, amplified by the inverter amplification section  210 , according to a gain set beforehand. 
     The functions of the inverter amplification section  210 , the impedance matching section  230 , and the amplification section  240  are similar with those of the inverter amplification section  110 , the impedance matching section  120 , and the amplification section  130  as described in  FIG. 1 . Thus, a detailed description thereof will be omitted. 
       FIG. 4  is a schematic circuit diagram illustrating the power amplifier as shown in  FIG. 4 . 
     Referring to  FIG. 4 , the configurations of first and second P-channel MOS FETs  211   a  and  212   a , included in the first inverter  211 , and first and second N-channel MOS FETs  211   b  and  212   b , included in the second inverter  212 , of the inverter amplification section  210  are the same as those of the inverter amplification section  110 . Thus, a detailed description thereof will be omitted. 
     The intermediate amplification section  220  may include first and second amplification units  221  and  222  that re-amplify signals having positive and negative levels, respectively, which are amplified by the inverter amplification section  210 . 
     The first amplification unit  221  may include first cascade amplification units  221   a  and  221   b  and first cascode amplification units  221   c  and  221   d  that are connected in series between a driving power terminal supplying driving power Vcc and ground. The second amplification unit  222  may include second cascade amplification units  222   a  and  222   b  and second cascode amplification units  222   c  and  222   d  that are connected in series between the driving power terminal and ground. 
     The first cascade amplification units  221   a  and  221   b  may include third and fourth P-channel MOS FETs  221   a  and  221   b , respectively, which are arranged in cascade configuration. The first cascode amplification units  221   c  and  221   d  may include third and fourth N-channel MOS FETs  221   c  and  221   d , respectively, which are arranged in cascode configuration. 
     The second cascade amplification units  222   a  and  222   b  may include fifth and sixth P-channel MOS FETs  222   a  and  222   b , respectively, which are arranged in cascade configuration. The second cascode amplification units  222   c  and  222   d  may include fifth and sixth N-channel MOS FETs  222   c  and  222   d , respectively, which are arranged in cascode configuration. 
     Since the above-described cascade configuration and cascode configuration are known in the art, a detailed description thereof will be omitted. 
     However, while one with a positive signal between the signals amplified by the inverter amplification section  210 , may be input to a gate of the third P-channel MOS FET  221   a  of the first cascade amplification units  221   a  and  221   b  and a gate of the fourth N-channel MOS FET  221   d  of the first cascode amplification units  221   c  and  221   d , the other signal with a negative signal between the signals, amplified by the inverter amplification section  210 , may be input to a gate of the fifth P-channel MOS FET  222   a  of the second cascade amplification units  222   a  and  222   b  and a gate of the sixth N-channel MOS FET  222   d  of the second cascode amplification units  222   c  and  222   d.    
     Furthermore, while a gate of the fourth P-channel MOS FET  221   b  of the first cascade amplification units  221   a  and  221   b  and a gate of the sixth P-channel MOS FET  222   b  of the second cascade amplification units  222   a  and  222   b  may be connected in common to each other, a gate of the third N-channel MOS FET  221   c  of the first cascode amplification units  221   c  and  221   d  and a gate of the fifth N-channel MOS FET  222   c  of the second cascode amplification units  222   c  and  222   d  may be connected in common to each other. 
     The impedance matching section  230  may include a primary coil P and a secondary coil S. One end of the primary coil P is electrically connected to a connection node between the fourth P-channel MOS FET  221   b  and the third N-channel MOS FET  221   c  and receives one of the re-amplified signals, which has a positive level. The other end of the primary coil P is electrically connected to a connection node between the sixth P-channel MOS FET  222   b  and the fifth N-channel MOS FET  222   c  and receives the other one of the re-amplified signals, which has a negative level. 
     The secondary coil S may perform the impedance matching of the signals with positive and negative levels according to a turns ratio determined by electromagnetic coupling between the primary coil P and the secondary coil S to thereby transmit the impedance-matched signals to the amplification section. 
     The amplification section  240  may include third and fourth cascode amplification units  241  and  242  that are connected in series between the driving power terminal and ground and are connected in parallel with each other. 
     The third cascode amplification unit  241  may include seventh and eighth N-channel MOS FETs  241   a  and  241   b  that are connected in cascode configuration between the driving power terminal and ground. The fourth cascode amplification unit  242  may include ninth and tenth N-channel MOS FETs  242   a  and  242   b  that are connected in cascode configuration between the driving power terminal and ground. 
     Since the above-described cascode configuration is known in the art, a detailed description thereof will be omitted. 
     However, the seventh and ninth N-channel MOS FETs  241   a  and  242   a  have gates that receive the impedance-matched signals having positive and negative levels, respectively, while the eighth and tenth N-channel MOS FETs  241   b  and  242   b  have gates that receive gain control signals VCG to control the gain. 
       FIG. 5  is a schematic circuit diagram illustrating a power amplifier according to another exemplary embodiment of the invention. 
     Referring to  FIGS. 4 and 5 , the connections and configurations of an intermediate amplification section  320  having P-channel MOS FETs  321   a ,  321   b ,  322   a , and  322 , an impedance matching section  330  having N-channel MOS FETs  321   c ,  321   d ,  322   c ,  322   d ,  341   a ,  341   b ,  342   a , and  342   b , and an amplification section  340  having a primary coil P and a secondary coil S, which are included in a power amplifier according to this embodiment, are the same as those of the power amplifier, as shown in  FIG. 4 . Thus, a detailed description thereof will be omitted. 
     An inverter amplification section  310  may include a first inverter  311  and a second inverter  312 . The first inverter  311  may include first and second inverter amplification units  311   a ,  311   b ,  311   c , and  311   d  that are connected in series between the driving power terminal and ground. The second inverter  312  may include third and fourth inverter amplification units  312   a ,  312   b ,  312   c , and  312   d  that are connected in series between the driving power terminal and ground. 
     The first inverter amplification sections  311   a  and  311   b  may include a first P-channel MOS FET  311   a  and a first N-channel MOS FET  311   b , respectively. The second inverter amplification sections  311   c  and  311   d  may include a second P-channel MOS FET  311   c  and a second N-channel MOS FET  311   d , respectively. 
     The third inverter amplification sections  312   a  and  312   b  may include a third P-channel MOS FET  312   a  and a third N-channel MOS FET  312   b . The fourth inverter amplification sections  312   c  and  312   d  may include a fourth P-channel MOS FET  312   c  and a fourth N-channel MOS FET  312   d.    
     An input signal RFin+ having a positive level, among RF input signals, may be input to the first and second inverter amplification units. An input signal RFin− having a negative level, among the RF input signals, may be input to the third and fourth inverter amplification units. 
     The input signal RFin+ having a positive level may be input to individual gates of the first P-channel MOS FET  311   a , the first N-channel MOS FET  311   b , the second P-channel MOS FET  311   c , and the second N-channel MOS FET  311   d . The input signal RFin− having a negative level may be input to individual gates of the third P-channel MOS FET  312   a , the third N-channel MOS FET  312   b , the fourth P-channel MOS FET  312   c , and the fourth N-channel MOS FET  312   d.    
     Furthermore, a source of the first N-channel MOS FET  311   b  may be connected to a drain of the second P-channel MOS FET  311   c , and a source of the third N-channel MOS FET  312   b  may be connected to a drain of the fourth P-channel MOS FET  312   c.    
     Since other connections, except for these connections, are similar with those of the inverter amplification section  110 , as shown in  FIG. 2 , a detailed description thereof will be omitted. 
     As described above, according to the exemplary embodiments of the invention, an RF input signal is amplified according to an inverter method to remove DC components therefrom, thereby preventing power consumption caused by a DC signal, so that the efficiency of power, being consumed by a power amplifier, can be increased. 
     As set forth above, according to exemplary embodiments of the invention, power consumption caused by DC components of an RF input signal is prevented to thereby increase the power efficiency of a power amplifier. 
     While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.