Low-temperature micropower CJFET OpAmp with reduced Vzero value

Abstract

The original circuitry of the operational amplifier (OpAmp) and its modifications based on complementary field-effect transistors with a control p-n junction (СJFET, JSC "Integral", Belarus) is considered. A feature of the proposed CJFET OpAmp scheme is the use of a special static mode stabilization circuit in the input differential stage and intermediate push-pull folded-cascode on identical uncontrolled JFET dynamic loads. Computer simulation of СJFET OpAmp in the LTSpice software environment (Analog Device, USA) was performed in a wide temperature range (from -197°С to 27°С) and exposure to a neutron flux (up to 1014 n/cm2). The proposed circuitry solutions increase the open-loop gain of the CJFET OpAmp to 75 dB and minimize the systematic component of the zero offset voltage (less than 600 μV). The mathematical analysis of the open-loop gain of the CJFET OpAmp is given in paper. The developed CJFET OpAmp circuitry is applicable in various analog and analog-to-digital interfaces (active RC-filters, normalizing converters, etc.) operating at low temperatures and exposure to radiation.