Implementation of a CMOS analog linear VGA

A novel structure for an analog linear variable gain amplifier (VGA) fabricated in CMOS 0.35μm technology is proposed in this paper. In order to increase noise performance and linearity, the VGA is designed based on differential topology. The pseudo-exponential gain is altered following the control of a current source supplied to a differential source-coupled pair with diode-connected loads. This VGA structure is adapted version of the one proposed in [1] to achieve better performance. The simulation and experiment results indicate that the continuous gain varies linearly in a range of -16.1 dB to 16.3 dB when the control voltage varies from -3.3 V to 2.1 V, the bandwidth of the proposed VGA is 994 MHz. The maximum deviation of the gain is roughly 0.5 dB as temperature fluctuates in the 0-80°C range, proving it robust to temperature variation.