Improvement of the signal‐to‐noise (S/N) ratio of cw NMR spectrometers by cooling circuit components to liquid helium temperature is discussed. Criteria for design of a low temperature circuit using a twin‐T bridge and MOSFET amplifier are presented. A liquid helium temperature spectrometer for operation at 16 MHz which improves S/N ratio by a factor of 5 over conventional techniques is described.