AUDIO TRANSMISSION CIRCUIT COMPRISING A TRANSMIT AMPLIFIER IN THE FORM OF A LINE VOLTAGE STABILISER

摘要

Transmit amplifier (1) which also stabilises the line direct voltage for the audio transmission circuit of a telephone set. By choosing according to the invention a suitable structure of the transmit amplifier (1) which functions at the same time as a line voltage stabiliser, the gain is variable by means of a resistor (15) which does not affect the further properties of the audio transmission circuit. A high gain is possible; spread in the line direct voltage by offset of the microphone pre-amplifier preceding the transmit amplifier and by temperature fluctuations of the reference voltage is greatly reduced in accordance with the invention by increasing the reference voltage and by adding a temperature-dependent current source (18).