A quasilinear wide-range radiometer amplifier implemented with correlated phase-sensitive detection

A radiometer amplifier capable of wide-range optical measurement is describ ed. Based on a novel automatically ranged electrometer and amplifier circui t, the radiometer provides a quasilinear analog output for the measurement of input radiation over ten orders of magnitude. Together with the scheme o f phase-sensitive detection of modulated optical signals, the circuit resul ted in an output voltage of low noise and offset drift. It can be applied d irectly to various kinds of photodetectors. The application of standard int egrated circuits and lock-in amplifiers makes the whole system low cost and it can be readily built. (C) 1999 American Institute of Physics. [S0034-67 48(99)04905-9].