VARIABLE GAIN AMPLIFIER CIRCUIT

摘要

PURPOSE:To improve output waveform distortion at the time of a low gain in an amplifier which by-passes the bias current of an amplifying transistor TR and varies in gain by inserting a diode and a resistance in series with the emitter of this TR. CONSTITUTION:A bias current is allowed by a current by-pass TR6 to by-pass an amplifying TR5. The diode D for improving waveform distortion and series feedback resistance RE are inserted in series with the emitter of the amplifying TR5. Consequently, the linear part of IC-VBE characteristics (not shown in a figure) of the amplifying TR5 is gentle and the output waveform distortion when the current IC is small, i.e. at the time of a low gain is improved. Further, peaking capacitors CP1 and CP2 are inserted in parallel to the diode D and feedback resistance RE to obtain a wide band.