A Wideband Variable-Gain Amplifier in 130 nm CMOS Technology

A VGA is used to provide a variable gain for input signals of varying strength. Hence VGAs have become crucial blocks in wireless transceiver sections. The ability of VGA to amplify signals of varying strength increases the dynamic range of the receiver. The effect of cascading on the parameters of variable gain amplifier (VGA) has been presented. The single stage VGA block is termed as "basic unit cell". The basic unit cell is a simple structure which can be cascaded to achieve more gain. The designed cascaded VGA has a large Bandwidth and low noise. Bandwidth of 3 GHz and a Noise Figure of 4 are measured. The cascaded VGA not only has a large gain but also a large linear gain range and very small gain error. A maximum gain of around 38 dB and a gain range of around 26 dB are achieved. Moreover the cascaded VGA only consumes few milli-amperes of current from a 1.2V supply. The robustness of the design is verified by means of ADS simulation.