This reliable, high input impedance, unity gain metal‐oxide‐semiconductor field‐effect transistor preamplifier is an improved design for cryogenic applications. The high input impedance is well suited for applications involving capacitive transducers. This circuit is directly immersible in liquid helium and thereby reduces the noise and spurious pickup associated with remotely located preamplifiers. In addition, the circuit utilizes easily available commercial parts which will reduce cost and the need to order nonstandard components.