Input current compensation for transistor operational amplifiers
J. N. Harris, R.S. Orr · SIMULATION · 1966
Abstract : The input current of transistor operational amplifiers limits their application for some uses. Several techniques are described which result in a substantial reduction of this input current. The resulting input current can range from 20% of the original current over a wide temperature span. The percentage reduction depends on the degree of complexity and precision of the compensating circuit used. One type of compensation uses a thermistor-resistor circuit. This technique is developed in detail--both analytically and experimentally, and various examples are given. For the case of a transistor having an input current of 50 nA, it is possible to design circuits to reduce this value to as little as 0.5 nA over a 50C temperature span.