Amplifier circuit designed for use in a bipolar integrated circuit, for amplifying an input signal selected by a switch circuit

摘要

PCT No. PCT/JP90/01311 Sec. 371 Date Jun. 10, 1991 Sec. 102(e) Date Jun. 10, 1991 PCT Filed Oct. 11, 1990.An amplifier circuit having a switch (SW), wherein the switch selects one of a plurality of input voltage-to-current converting amplifiers (GM1 to GMn), and the input amplifier, thus selected, converts an input signal into a current. This current is added to a feedback signal current. Hence, even if the signals input to the voltage-to-current converting amplifiers have different DC potentials, the DC potential difference does not appear in the output. The DC potential of the output signal of the amplifier circuit is determined by the reference voltage (VREF) of a feedback voltage-to-current amplifier (GMNF) and hence remains constant at all times.