Design of variable gain amplifier in CMOS technology
Date of Issue2015
School of Electrical and Electronic Engineering
Centre for Integrated Circuits and Systems
Virtus,IC Design Centre of Excellence
The variable gain amplifier (VGA), as one of the critical components in modern wireless transceiver designs, is widely used to provide a fixed output power for different input signals to improve the transceiver’s dynamic range. Based on the targeted frequency, VGA is categorized as general purpose VGA for narrow bandwidth applications, and high-frequency VGA for applications with stringent bandwidth requirement. The challenges in VGA design is mainly the realization of accurate dB-linear characteristic with minimum power consumption and die area, as well as achieving the required bandwidth for the targeted application. In this thesis, a new design approach which is the “cell-based” design method is proposed. The advantage of cell-based VGA design is that the number of unit cells to be cascaded can be chosen according to the system requirements. Moreover, a reconfigurable approach, by means of a digital control, can be implemented based on the unit cell to realize re-configurability and power scalability. As a result, multiple application standards can be satisfied with options for wide gain variation range, small gain error or low power consumption. There are mainly two types of cells designed for the proposed cell-based design method. One is the gate-tuned VGA cell and the other one is the body-tuned VGA cell. Both of the cells achieved accurate dB-linear characteristic with minimum power consumption. The gate-tuned VGA cell is also combined with gate peaking technique for bandwidth extension, such that it is suitable in high-frequency VGA design. Based on the proposed cells, three VGAs are designed, which are a gate-tuned general purpose VGA, a body-tuned general purpose VGA and a gate-tuned high-frequency VGA with gate peaking technique. Measurement results show that the proposed cell-based design method is not only feasible, but also achieved very good performance in terms of accuracy, bandwidth, power consumption and die area. The body-tuned reconfigurable VGA can also work as a tunable PGA with variable gain step, which demonstrated the re-configurability, power scalability and versatility of the proposed cell-based design method.
DRNTU::Engineering::Electrical and electronic engineering::Integrated circuits