Correlator-Amplifier for Very Low Level Signals

A correlator-amplifier system based on a Hall multiplier improves the sensitivity of low level amplifiers by two to three orders of magnitude. The system is assembled largely from commercial instruments, with the exception of the Hall element itself. Over the frequency interval from 10 cps to 10 kc, the equivalent input noise level ranges from 5×10−15 to 10−19 V2/cycle. The system is capable of detecting correlated signals presented to both inputs in the presence of uncorrelated noise two to three orders of magnitude greater.