In certain applications a picoampere‐range current comparator with a wide range of input currents is needed. This paper presents a simple current comparator realized using gate‐source and gate‐substrate junctions of a dual junction field effect transistor (JFET) as current‐to‐voltage converters to control the circuit. Measurements using an AD 833A JFET have been carried out with input currents in the range 0.1–100 pA and drain voltages in the range 100 mV–10 V.