| 摘要 |
PROBLEM TO BE SOLVED: To provide an amplifier circuit which can suppress the leakage current of a signal input terminal and also can keep a high input impedance. SOLUTION: The base of a transistor TR Q21 is connected to the base of a TR Q1 and a current is generated by the TR Q21 corresponding to the input signal. The current is generated by TR Q20 and Q12, respectively corresponding to the emitter current of the TR Q21. Then a current mirror consisting of the TR Q13 and Q14 generates a compensating current ICO1 in accordance with the base current of the TR Q12 at the collector of the TR Q14. The size of each TR of a current compensating circuit is controlled and the current ICO1 is set equal to the sum of base currents of both TR Q1 and Q21. Thus, the base currents of the TR Q1 and Q21 can be compensated. In such a constitution, this amplifier circuit can suppress the leakage current of a signal input terminal and also can keep a high input impedance.
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