Variable impedance circuit

Abstract

Abstract PURPOSE:To realize floating type variable impedance with excellent linearity by using a differential transistor couple. CONSTITUTION:A couple of differential transistors 10 are provided with constant current sources 11, 12 and 13, which supply currents at a ratio of 1:1:2. Connecting signal source 6 to terminal 1 flows input current (i1) through transistor Q11, allowing corresponding current ICto flow. At this time, current IC) flows out from constant current source 12 and output current (i2) equivalent to input current to input current (i1) is obtained. In this case, potential difference (vR) between terminals 1 and 2 is determined by the input current and IC and made unrelated to the earth potential. Therefore, a floating type variable impedance circuit is realized between terminals 1 and 2. In addition, it is possible to insert a couple of PN junctions between emitter electrodes of transistors Q11 and Q12 in order to obtain wide linearity.

Inventors

• 👤 Masayuki Katakura

Bibliographic Details