High-gain differential amplifier

Claim 1

An electronic signal amplifier comprising: first and second input transistors, first and second regulating transistors, output means comprising at least one output transistor, each of said transistors having base, emitter and collector electrodes, low impedance means for directly connecting a collector-emitter conduction path of each of said input transistors in series relation with a collector-emitter conduction path of a corresponding one of said regulating transistors, means for coupling input signals to the base of at least one of said input transistors, means for direct current coupling a point intermediate the emitter of said first input transistor and the collector of said first regulating transistor to a point intermediate the emitter of said second input transistor and the collector of said second regulating transistors, feedback means coupled from each of said input transistors to a corresponding one of said regulating transistors for varying current in said regulating transistor collector-emitter paths in response to input signals while tending to reduce variations, from a quiescent value, of current in said collector-emitter paths of said input transistors, means for coupling the base-emitter circuit of said output transistors in parallel with the base emitter circuit of one of said regulating transistors such that the same signal is supplied to said parallel-coupled base-emitter circuits of said output and regulating transistors, and means coupling a load impedance to the collector-emitter path of said output transistor for producing a substantially linearly amplified replica of said input signals, the voltage gain of said amplifier being determined by the ratio of said load impedance to the impedance at said point associated with the collector of said one regulating transistor.