A stabilized amplifier for measurement purposes

This paper describes a stabilized amplifier with an over-all amplification ratio that remains essentially constant in magnitude and phase for all changes in tube characteristics, line-voltage variations, and output load variations to be expected during normal operation. This stability is obtained by the introduction of two stabilizing circuits which act independently, yet are complementary when used together. During a period of eight weeks´ use two such amplifiers with their associated indicating instruments maintained their original calibration within two-tenths per cent of full scale without readjustment.