Reducing noise in photoamplifier circuits with low noise artificial resistors

A standard passive dissipative resistor in a photodiode circuit is replaced by a low-noise active artificial resistor. A room-temperature artificial resistor acts on a signal current from the photodiode in the same manner as the resistor, but the self-generated noise of the artificial resistor is that of a resistor at cryogenic temperatures. Because of its low noise, the artificial resistor can produce an improvement in the signal to noise of the photodetector system with minimum effect on the bandwidth. Analysis shows that the system signal to noise can approach that of the photodiode itself. An experiment designed to demonstrate the effect produced an improvement of 2.8 dB in a photoamplifier circuit.