A 2N3819 FET provides a solid-state VOM. The 2N3819 acts as a cathode follower in a VOM. The bias offset (meter null) is obtained with R14 and R12 sets full-scale calibration. R2 through R9 should total about 10 M ohm. R10 is a protective resistor, and C2 provides ac bypassing to limit RF and noise pickup.

The Circuit Diagram of Fet Voltmeter