The U421 is a high input impedance Monolithic Dual N-Channel JFET
Linear Systems replaces discontinued Siliconix U421

The U421 monolithic dual n-channel JFET is designed to provide very high input impedance for differential amplification and impedance matching. Among its many unique features, this series offers operating gate current specified at -250 fA. The U421 is a direct replacement for discontinued Siliconix U421.

FEATURES
    HIGH INPUT IMPEDANCE IG = 0.25pA MAX
    HIGH GAIN gfs = 120µmho MIN
    LOW POWER OPERATION VGS(OFF) = 2V MAX

U421 Applications:
▪ Ultra Low Input Current Differential Amps
▪ High-Speed Comparators
▪ Impedance Converters