JPS56162519A - Amplifier - Google Patents

Abstract

PURPOSE:To amplify AC signals by holding an input and output DC voltage nearly equal by feeding transistors, whose emitters are connected together mutually and which are supplied with the 1st and 2nd AC signals and by outputting AC signals via a transistor having the same porality. CONSTITUTION:A biasing circuit 1 extracts the voltage D of diodes 3-5 and applies it to an NPN transistor (TR)7. An input signal, applied to the base point A of the TR7, appears at the collector of TR7 with the opposite phase and is applied to a PNP TR11. Therefore, the collector output of the TR11 is in phase. A signal applied to the base of the TR7, on the other hand, appears at emitters of TRs 7 and 8 with the same phase, an inphase amplification output is obtained at the collector of the TR8, and an output signal appears at a terminal C from the connection point of collectors of the TRs 8 and 11 via a TR12. The DC bias at the base of TR7 is nearly equal to the voltage D and base currents of the TRs 7 and 8 are small, so a voltage drop across a resistance 14, nearly equalizing base voltages of the TRs 7 and 8 to the emitter voltage of the TR12.