VOLTAGE CURRENT AMPLIFYING CIRCUIT HAVING SPECIFIED INPUT IMPEDANCE AND VARIOUS MUTUAL CONDUCTANCE

摘要

PURPOSE: To obtain amplifier circuits having a prescribed input impedance and different mutual conductance by providing a 1st and a 2nd parabasic circuits between an input, and a 1st and a 2nd output terminals. CONSTITUTION: The parabasic circuits B1 and B2 are provided with a differential amplifier D of which the input D1 is connected to a combination capacitor C via a resistor R4 and the output terminal is connected to the input E of this circuit, and provided with a transistor T of which the base is connected to the output D3 of the differential amplifier D, and a switch K1 formed by a transistor which is set in a saturation state when the switch is turned on. Then, the parabasic circuits B1 and B2 are provided with an amplifier A1/A2, the emitter of the corresponding transistor, a resistor R2a/R2b which is connected between the input and the 1st input D1 of the corresponding differential amplifier D, and a switch K2 which is set in a saturation state when the switch is turned on, respectively. Thus, the prescribed input impedance is obtained without an additional pad, and two optimized different conductance is given to each head.