DIFFERENTIAL AMPLIFIER CIRCUIT

摘要

PURPOSE:To suppress an increase in distortion and decrease in output by preventing modulation output from being saturated by the common connection point of emitters of 1st and 2nd transistors to a current sucking-out terminal via current source varying in a monotone. CONSTITUTION:Transistor Tr1 is applied with an AM signal at its base, Tr2 is also applied at its base with an AM signal out of phase with the AM signal or a DC voltage, and the collector of TR2 is connected to output terminal 11 via resistance 8. Common connection point X of emitters of Tr1 and Tr2 is connected to current sucking-out terminal 15 via current source 14 which varies monotonously in inversely-relative current according to an increase or decrease in the mean value of output voltages developed at output terminals 5 and 6 or in the mean value of the difference of output voltage. Consequently, even when a strong AM signal arrives, the saturation of modulation output is prevented and an increase in distortion and decrease in output can be suppressed.