High input resistance circuit with base current compensation and method of compensating base current

摘要

A high input resistance circuit that produces an output signal with a voltage gain of unity includes an input section, a feedback section, a high input resistance amplification section, and an output section. In the input section, transistors 1.sub.a and 1.sub.b form a differential amplification circuit using transistors 2.sub.a and 2.sub.b as emitter resistors, respectively. A feedback circuit is formed by transistors 3. sub.a and 3.sub.b whose collectors are connected to bases of transistors 1.sub.a, 1.sub.b, respectively, and whose emitters are connected to the collector of transistor 8.sub.b of the output section. The bases of transistors 3.sub.a and 3.sub.b are provided a bias from a bias terminal 106 so as to suppress a collector current. In the high input resistance amplification section, transistors 4.sub.a and 4.sub.b form an emitter follower circuit using transistors 5.sub.a, 5.sub.b and resistors R.sub.1, R.sub.2 as emitter resistors, respectively. In the output section, transistors 6.sub.a and 6.sub.b form a differential amplification circuit, wherein the collectors of transistors 6.sub.a and 6.sub.b are connected to a current mirror circuit having transistors 8. sub.a and 8.sub.b, and the emitters of transistors 6.sub.a and 6.sub.b are connected to an emitter load resistor consisting of transistors 7.sub. a, 7.sub.b and resistors R.sub.4, R.sub.5.