A temperature compensated 100 MHz to 1 GHz variable gain amplifier in a 8 GHz 1.2 μm BiCMOS process

A variable gain amplifier with linear gain control has been implemented in a commercially available 8 GHz 1.2 μm BiCMOS process. The gain adjustment linearization is based on forcing a linearly controllable current through diode-connected transistors, thus generating an internal logarithmic control voltage for a Gilbert-type variable gain cell. A cascode type gain stage is used to provide most of the available gain. PTAT and bandgap type references are used to stabilize the gain against changes in operating conditions. Thus, the maximum simulated differential gain of 18 dB varies less than 1 dB over temperature range from -10°C to 85°C. The circuit has a simulated bandwidth of over 1 GHz and 2 dBm output -1 dB compression power with expected gain adjustment range of 50 dB. The chip area is 1.15×2.00 mm and it consumes 100 mA from a 5 V supply