ICs Provide HEMT FET Biasing

Handling three, four or six FET stages, respectively, ZNBG 3000, 4000 and 6000 series ICs are designed to provide all the bias requirements of GaAs and HEMT FETs in point-to-point applications. Operating from a single positive supply, the devices generate the negative 3V rail required for FET gate biasing. Working with two capacitors and resistors, the FET bias controller ICs produce the drain voltage and current control needed by the externally grounded FETs. They also let designers split the control conditions of individual FET gate stages. Therefore, the operating current of the input FETs can be set to achieve the lowest noise and following FET stages can be independently regulated for maximum gain. ZNBG 3000, 4000 and 6000 ICs deliver 2.2V drain, while ZNBG 3001, 4001 and 6001 provide 2V. Gate drive from the bias circuits is restricted to from -3.5V to 0.7V to protect gates from transients. If the negative rail fails, the drain supply is shut down to avoid excessive current flow.