Gigahertz-band high-gain low-noise AGC amplifiers in fine-line NMOS

The design and test results of a single-chip NMOS automatic gain control (AGC) amplifier are described. The amplifier has a maximum flat gain of 50 dB, dynamic range of 70 dB, and a noise figure of 11 dB. The flat response from near DC to a 3-dB bandwidth of 1 GHz does not require tuning of any peaking circuits. The chip is also capable of operating at 3 GHz with unity gain delivering -8 dBm into a 50-/spl Omega/ load. The global feedback scheme designed for this chip stabilizes it against large shifts in threshold voltage and ambient temperature variation of 170/spl deg/C. This feedback scheme can provide stable DC feedback for a forward amplifier gain of at least 60 dB. Application of this application in the design of low-noise high-speed fibre-optic systems is envisaged.