| 摘要 |
PURPOSE:To make the input impedance constant, by supplying a constant current to a transistor (TR) having the same characteristics as an input TR and compensating the increase/decrease in the base current of the input TR via a current mirror circuit. CONSTITUTION:A constant power supply 15 having a half value a constant current source 8 comprising Trs 3, 4 is connected to the emitter of a PNP TR14 having the same characteristics as PNP TRs 3, 4 constituting a part of an input circuit of a comparison circuit. The base current of the TR14 is taken as a sink current for TRs 11, 12 forming a current mirror circuit 16 and each emitter current of Trs 1, 2 of the input circuit is set to a constant value. The increase/decrease of the base current of the PNP Trs 3, 4 is compensated to keep a constant value. |
