Design Of Variable Gain Amplifier In Quartz Gyroscope Driving Circuit

As the important part of automatic gain control (AGC) system,variable gainamplifier (VGA) has been widely used in communication, satellite launching，dataswitch and other correlative fields. With VGA, quartz gyroscope’s (QRS) driving circuitcan drive quartz gyroscope in sine wave. More over sine wave driving circuit which hashigh stability, high integration and high precision, can improve the QRS stability andresolving rate. So design of VGA which has a high performance has significance forimproving the whole performance of QRS driving circuit.This paper start with the principle of QRS, study deeply the driving principle of thesine driving circuit. Then the paper analyzes common VGA structures and introducesindicators which affect VGA performance.After theoretical analysis, this issue begin todesign the circuit of the selected structure.This paper adopts single-stage amplifier andexponential gain control circuit to achieve gain variation. The single-stage amplifieruses improved Gilbert to increase the gain and bandwidth, and reduce the powerconsumption and voltage redundancy. The exponential gain control circuit based oncorrected exponential function to approach ideal exponential function, and supply widecontrol voltage range.This paper based on0.5μm CMOS process library, using Hspice and Cadencesoftware to design and simulate the VGA. The system works at the5V supply voltage,and when load capacitance is taken5pF,the simulation results show that the VGA has3MHz bandwidth, non-distortion control voltage range is2.2V~2.7V, gain dynamicrange can reach-40dB~+30dB.