A low-drift integrating amplifier

Abstract

The need occasionally arises for a device performing an integration; situations may arise where limited size is a design objective,, The integrating feedback amplifier presents attractive possibilities. It is critically assessed.

A first model was constructed to focus more clearly the problems of drift and miniaturization possibilities. Experience enabled construction of a superior model with an output drift of less than 100 millivolts during hour-long trials as an integrator with a gain of 1 volt / sec /volt , Operation with 4^00 cycle filament supply was satisfactory. Power supply fluctuations produced equivalent spurious signals decreased in a ratio of 1000 : 1.

To combat zero-drift, the advanced technique of automatic stabilization (Goldberg Circuit) is employed, requiring consideration of miniature synchronous converters. To miniaturize the computing condenser without sacrifice of drift or quality of integration, grid current is controlled.

The power supply requirements are considered simple for a -100 volt output range. This was accomplished without sacrifice of gain by the use of gas-discharge tube coupling at low currents. All stages are stabilized to minimize effects of supply variation. The resulting high-gain low-drift integrating amplifier built in terms of miniature components is recommended as a prototype for further development in subminiature form.