High performance programmable gain amplifier designs

Abstract

The automatic gain control (AGC) circuit is an important building block of many systems. A function of the AGC loop, especially in wireless applications, is to automatically adjust the gain of the receiver path so that the signal at the input of the AD converter appears constant regardless of the signal level at the antenna. A variable gain amplifier (VGA) is a key block of AGC loops that are based on both feed-back and feed-forward approaches. While many high-performance VGAs have been implemented successfully with continuous-mode gain variation, with most applications, the VGAs are controlled by various digital circuitries or digital signal processing (DSP) units. Therefore, digitally controlled VGAs (i.e., Programmable Gain Amplifiers) save the need for auxiliary digital-to-analog converters. In this dissertation, design techniques for high performance CMOS-based programmable gain amplifier which features wide dynamic gain range, wide bandwidth, low power consumption, low voltage operation, process/temperature independences, and small chip area are presented. Firstly, a new gain control scheme for wider dynamic gain rage, insensitive to process/temperature variations and a new PGA architecture for power and chip area saving are introduced. Secondly, a new reconfiguration method that consists of two version: all-NMOS transistor and complementary PMOS/NMOS transistor is proposed to further extend the dynamic gain range of single PGA stages while saving chip size and power consumption. The next contribution is a low voltage, low power, high performance PGA using current-reused differential pair. A PGA was designed in 0.18$\mum$ CMOS TSMC to operate under 1.2V to verify the technique. In the forth contribution, a new transconductor that combines an inverter-based differential pair with an adaptive biasing circuit to reduce noise and distortion was analyzed. Based on the inverter-based differential with adaptive biasing (IDPAB) transconductor, a high linearity ...