Design Of Low-Voltage And Low-Power CMOS Programmable Gain Amplifier For Wireless Sensor Network

Wireless Sensor Network (WSN) technology is a thriving and interdisciplinary technology which combines wireless communication, computer science and sensor technology. It can sense and process information of individual node and realize communication between nodes through wireless transceivers. As a critical part of the transmission link, programmable gain amplifier (PGA) accommodates gain to change linearly based on the amplitude of input signals in order to achieve constant amplitude at output ports, making sure the receiver can demodulate signals correctly.This paper presents a design and realization of a low-voltage, low-power programmable gain amplifier for Wireless Sensor Network (WSN) application in 0.18μm CMOS process. The circuit operates under 1V voltage to achieve energy saving of WSN. According to IEEE 802.15.4 protocol, this PGA gain is variable in the range from OdB to 70dB with 2dB step, so cascaded amplifiers were adopted as a system architecture which consisted of fixed amplifiers and variable amplifier. Individual amplifier was connected by ac couple and switches to eliminate dc offset and bypass certain amplifiers which were not working to decrease power respectively. Fixed gain stage was a two-stage amplifier with gm-boosting and determined by the ratio of two resistors. As the last gain controller, the variable gain stage was a closed loop which allowed large input signals to improve linearity of the whole system. Switchable feedback resistors realized variable gains. The digital unit made gain programmable with a step of 2dB. The whole process covering circuit design, layout design, stimulation and test results was given in this paper. Test results show this PGA gain adjusts between 6.32dB and 74.45dB within a range from 0.5MHz to 3.5MHz. The swing amplitude of differential output reaches 0.72V and the input 1dB compression point @0dB is -7dBm. The PGA consumes 1.37mW under the supply of 1V.The performance of PGA basically meets the requirement so it can be used in the wireless transceiver for WSN application.