Signal-processing circuit having a field-effect MOSFET and bipolar transistors

摘要

The signal-processing circuit of the present invention, more particularly the gain-controlled amplifier circuit, comprises a MOSFET (metal oxide semiconductor field-effect transistor), and an NPN bipolar transistor cascade-connected to the MOSFET. The gain-controlled amplifier circuit amplifiers the signal supplied to the gate of the MOSFET, with the gain corresponding to the voltage applied to the base of the NPN bipolar transistor. The circuit can generate an output signal at one end of the emitter-collector path of the NPN bipolar transistor, said output signal containing negligibly small distortion components; in particular, negligible third distortion components.