Audio-frequency power amplifiers

A low-frequency power amplifier comprising:

• a pair of output transistors which are opposite in a conduction type to each other and each having an input electrode, an output electrode and a common electrode,
• a load connected between said output electrodes of said paired output transistors and a reference potential point,
• a first d.c. supply source connected between the common electrode of one of said paired output transistors and said reference potential point,
• a second d.c. supply source connected between the common electrode of the other of said paired output transistors and said reference potential point,
• means for supplying an input signal to each of the input electrodes of said paired output transistors,
• an impedance element connected between the input electrodes of said paired output transistors,
• a current stabilizer transistor having an input electrode, an output electrode and a common electrode,
• means for applying a bias voltage across the input and the common electrode of said current stabilizer transistor,
• means for supplying an output current from said current stabilizer transistor to said impedance element,
• a first resistor connected between the common electrode of said current stabilizer transistor and said first d.c. supply source, and
• a second resistor connected between the common electrode of said current stabilizer transistor and said second d.c. supply source.

A low-frequency power amplifier comprising:

• a pair of output transistors which are opposite in a conduction type to each other, each having a base electrode, an emitter electrode and a collector electrode,
• a load connected between the emitter electrodes of said paired output transistors and a reference potential point,
• a first d.c. supply source connected between the collector electrode of one of said paired output transistors and said reference potential point,
• a second d.c. supply source connected between the collector electrode of the other of said paired output transistors and said reference potential point,
• an impedance element connected between the base electrodes of said paired output transistors,
• means for supplying a signal to each of said base electrodes of said paired output transistors,
• a current stabilizer transistor having a base electrode, an emitter electrode and a collector electrode,
• means for supplying the collector current of said current stabilizer transistor to said impedance element,
• means for supplying a bias voltage across the base and the emitter electrode of said current stabilizer transistor,
• a first resistor connected between the emitter electrode of said current stabilizer transistor and said first d.c. supply source, and
• a second resistor connected between the emitter electrode of said current stabilizer transistor and said second d.c. supply source.

A low-frequency power amplifier comprising:

• a first transistor having a base electrode adapted to be supplied with a signal, an emitter electrode and a collector electrode which is adapted for producing an output signal,
• a second transistor having a base electrode which is d.c. coupled to the collector electrode of said first transistor, an emitter electrode and a collector electrode adapted for producing an output signal,
• third and fourth transistors which are opposite in a conduction type to each other, each having a base electrode, an emitter electrode adapted to produce an output signal and a collector electrode,
• an impedance element connected between the base electrodes of said third and fourth transistors,
• means for d.c. coupling the base electrode of said third transistor and the collector electrode of said second transistor to each other,
• a d.c. supply source connected between the collector electrodes of said third and fourth transistors and having a mid-point connected to a reference potential point,
• a first resistor connected between the emitter electrode of said first transistor and one pole of said d.c. supply source,
• second and third resistors connected in series to each other,
• means for d.c. coupling said second and third resistors between the emitter electrode of said first transistor and the other pole of said d.c. supply source, and
• a Zener diode connected between the junction of said second and third resistors and said reference potential point.

A low-frequency power amplifier comprising:

• a first transistor having a base electrode adapted to be supplied with a signal, an emitter electrode and a collector electrode which is adapted for producing an output signal,
• a second transistor having a base electrode which is d.c. coupled to the collector electrode of said first transistor, an emitter electrode and a collector electrode adapted for producing an output signal,
• third and fourth transistors which are opposite in a conduction type to each other, each having a base electrode, an emitter electrode adapted for producing an output signal and a collector electrode,
• an impedance element connected between the base electrodes of said third and fourth transistors,
• means for d.c. coupling the collector electrode of said second transistor to the base electrode of said third transistor,
• a d.c. supply source connected between the collector electrodes of said third and fourth transistors and having a mid-point connected to a reference potential point,
• means for supplying a bias voltage across the base and emitter electrodes of said first transistor,
• a first resistor connected between the emitter electrode of said second transistor and one pole of said d.c. supply source, and
• a second resistor connected between the emitter electrode of said second transistor and the other pole of said d.c. supply source.