ZNBR6000

FET BIAS CONTROLLER DRAFT ISSUE A - DECEMBER 2000 DEVICE DESCRIPTION The ZNBR series of devices are designed to meet the bias requirements of GaAs and HEMT FETs commonly used in satellite receiver LNBs, PMR, cellular telephones etc. with a minimum of external components and a VCC of 3-6V for improved efficiency. With the addition of two capacitors and resistors the devices provide drain voltage and current control for a number of external grounded source FETs, generating the regulated negative rail required for FET gate biasing whilst operating from a single supply. This negative bias, at -3 volts, can also be used to supply other external circuits. The ZNBR4000/1 and ZNBR6000/1 contain four and six bias stages respectively. In setting drain current the ZNBR4000/1 two resistors allows individual FET pair control to different levels, the ZNBR6000/1 two resistors split control between two and four FETs. This allows the operating current of input FETs to be adjusted to minimise noise, whilst the following FET stages can separately be adjusted for maximum gain. The series also offers the choice of drain v o lta g e t o b e s e t f or t he F E Ts, the ZNBR4000/6000 gives 2.2 volts drain whilst the ZNBR4001/6001 gives 2 volts. ZNBR4000 ZNBR4001 ZNBR6000 ZNBR6001 These devices are unconditionally stable over the full working temperature with the FETs in place, subject to the inclusion of the recommended gate and drain capacitors. These ensure RF stability and minimal injected nois...