In this paper, the design of variable gain ampli.er (VGA) for wireless receiver applications is presented. The VGA uses ac coupling (highpass filter) for dc offset rejection, while each VGA stage is designed to have constant output offset to overcome the slow response of the highpass filter. Due to the architecture chosen, The VGA has a fairly constant bandwidth in the entire gain range, and therefore it has constant settling time. It has been simulated and laid out using IBM SiGe BiCMOS 0.25Ām process. The VGA is OpAmp-R based and has gain range of -4 → 64dB with 2dB steps. It has about 35MHz bandwidth and consumes 1.5mA from 2.5V supply.
['Ahmed Emira', 'Edgar Sánchez-Sinencio']
Variable gain amplifier with offset cancellation