A Review of CMOS Variable Gain Amplifiers and Programmable Gain Amplifiers

CMOS implementations of variable gain amplifiers (VGAs) and programmable gain amplifiers (PGAs) are reviewed in this paper. They fall into two categories: Radio Frequency VGA/PGAs and Intermediate Frequency VGA/PGAs. Most approaches to realize gain tuning create linear VGAs and consequently exponential conversion are required. The CMOS circuit realizations of exponential converters are complex and are also reviewed. In contrast, PGAs benefit from their flexible gain control mode and hence have much simpler structures. However, lower distortions and higher gain accuracy can be achieved for PGAs. Therefore, PGAs are preferred in most scenarios. This paper also presents a CMOS Gilbert VGA and a novel high linearity constant bandwidth PGA with improved common mode rejection. The DC-offset cancellation methods are reviewed as well. Finally, trends of VGAs/PGAs in modern receivers are analysed.