Amplifier circuit

Claim 2

An amplifier circuit having a voltage-ampli­fying stage (3) for amplifying the voltage of an input signals, an output stage (9) including a push-pull cir­cuit comprising at least one complementary pair of output transistors (11, 12; 41, 42), and a drive stage (4) for driving the output transistors (11, 12; 41, 42) in response to an output of said voltage-amplifying stage (3), characterized in that: said drive stage (4) comprises reference voltage-­generating means (5) for generating a predetermined reference voltage, subtracting means (6) for generating a voltage corresponding to the differences between the reference voltage and the output voltage of said voltage-amplifying stage (3), which is based on a first pole-potential of a power supply, and signal-converting means (7, 8) for converting the output voltage of said subtracting means (6) to a voltage signal based on a second pole-potential of the power supply, and supplying the voltage signal to said output stage (9); and one (11; 41) of the output transistors of said output stage is driven by the voltage signal supplied from said signal-converting means (7, 8), and the other output transistor (12; 42) is driven by the output voltage of said voltage-amplifying stage (3).

Claim 3

An amplifier circuit according to claim 1, characterized in that said output stage (9) has a comple­mentary push-pull circuit including a pair of output transistors (11, 12; 41, 42) which are of the first and second conductivity types, respectively, and each have a first electrode for supplying carriers, a second electrode for taking the carriers out and a third electrode for controlling a flow of the carriers, are connected at the first electrode to first and second potential points of said power supply, respectively, and at the second electrode to each other, thus forming a node from which an output is supplied, said output voltage of said voltage-amplifying stage (3) being applied between the first and third electrodes of the output transistor (12; 42) of the second conductivity type; said reference voltage-generating means (5) comprises transistors (21, 22; 51, 52) of the second conductivity type; said subtracting means (6) comprises transistors (23, 24; 53, 54) of the second conductivity type; and said signal-converting means includes voltage-to-current converting means (7) comprised of a transistor (25, 55) of the second conductivity type for outputting a current corresponding to the output voltage of said subtracting means (6), and current-to-voltage converting means (8) comprised of a transistor (26; 56) of the first conductivity type for generating a voltage corresponding to the output current of said voltage-­to-current converting means (7), and designed to apply said voltage between the first and third electrodes of said output transistor (11; 41) of the first con­ductivity.

Claim 4

An amplifier circuit according to claim 2, characterized in that the transistors of the first conductivity type are PMOSFETs, the transistors of the second conductivity type are NMOSFETs, and the first, second and third electrodes are a source, a drain and a gate, respectively.

Claim 5

An amplifier circuit according to claim 2, characterized in that the transistors of the first conductivity type are PNP bipolar transistors, the transistors of the second conductivity type are NPN bipolar transistors, and the first, second and third electrodes are an emitter, a collector and a base, respectively.

Claim 6

An amplifier circuit according to claim 2, characterized in that said reference voltage-gene­rating means (5) comprises a circuit having two diode-connected transistors (21, 22; 51, 52) of the second conductivity type connected in series to each other, and a constant current source (20) for supplying a constant DC to these two transistors (21, 22; 51, 52), and using a node of said constant current source and one (21; 51) of said two transistors as an output terminal; said subtracting means (6) comprises a circuit having two transistors (23, 24; 53, 54) of the second conductivity type and using a node of the first electrode of one (23; 53) of these two transistors and the second electrode of the other (24; 54) of these two transistors as an output terminal, one (23; 53) of said two transistors being connected at the second and third electrodes to a first potential point and the output terminal of said reference voltage-generating means (5), respectively, and the other (24; 54) of said two transistors being connected at the second and third electrodes to the first electrode of said one transistor and the output terminal of said voltage-amplifying stage (3), respectively; said voltage-to-current converting means (7) comprises a circuit having a transistor (25; 55) of the second conductivity type and using the second electrode of this transistor as an output terminal, said transistor (25; 55) being connected at the first electrode to a second potential point and at the third electrode to the output terminal of said subtracting means (6); and said current-to-­voltage converting means (8) comprises a circuit having a transistor (26; 56) of the first conductivity type and using a node of the second and third electrodes of this transistor (26; 56) as an output terminal, said transistor (26; 56) being connected at the second and third electrodes to the second electrode of the transistor (25; 55) of said voltage-to-current convert­ing means (7), at the first electrode to said first potential point, and at the third electrode to the third electrode of said output transistor (11; 41) of the first conductivity type.

Claim 7

An amplifier circuit according to claim 5, characterized in that the transistors of the first conductivity type are PMOSFETs, the transistors of the second conductivity type are NMOSFETs, and the first, second and third electrodes are a source, a drain and a gate, respectively.

Claim 8

An amplifier circuit according to claim 5, characterized in that the transistors of the first conductivity type are PNP bipolar transistors, the transistors of the second conductivity type are NPN bipolar transistors, and the first, second and third electrodes are an emitter, a collector and a base, respectively.

Claim 9

An amplifier circuit according to claim 5, characterized in that a high-impedance element (30) is connected between the output terminal of said subtracting means (6) and said first potential point for pulling up the potential of the output terminal of said subtracting means (6).

Claim 10

An amplifier circuit according to claim 8, characterized in that the transistors of the first conductivity type are PMOSFETs, the transistors of the second conductivity type are NMOSFETs, and the first, second and third electrodes are a source, a drain and a gate, respectively.

Claim 11

An amplifier circuit according to claim 8, characterized in that the transistors of the first conductivity type are PNP bipolar transistors, the transistors of the second conductivity type are NPN bipolar transistors, and the first, second and third electrodes are an emitter, a collector and a base, respectively.

Claim 12

An amplifier circuit according to claim 2, characterized in that a first control transistor (27; 57) of the first conductivity type is connected at a first electrode to the first potential point, and at a second electrode to the third electrode of the output transistor (11; 41) of the first conductivity type, said first control transistor (27; 57) being turned on to render the output transistor non-conductive when it is unnecessary to supply the output of the amplifier cir­cuit to a load; and a second control transistor (28; 58) of the second conductivity type is connected at a first electrode to the second potential point, and at a second electrode to a third electrode of said output transistor (12; 42) of the second conductivity type, said second control transistor (28; 58) being turned on to render this output transistor (12; 42) non-conduc­tive in cooperation with said first control transistor (27; 57), when it is unnecessary to supply the output of the amplifier circuit.

Claim 13

An amplifier circuit according to claim 11, characterized in that the transistors of the first conductivity type are PMOSFETs, the transistors of the second conductivity type of NMOSFETs, and the first, second and third electrodes are a source, a drain and a gate, respectively.

Claim 14

An amplifier circuit according to claim 11, characterized in that the transistors of the first conductivity type are PNP bipolar transistors, the transistors of the second conductivity type are NPN bipolar transistors, and the first, second and third electrodes are an emitter, a collector and a base, respectively.