Design of Variable Gain Amplifier Based on the 0.18 μm Bipolar Process
As the front-end core module of a receiver system,a variable gain amplifier can adjust the gain,stabilize the power,and adjust the dynamic range of a signal.Its performance directly affects core technical indicators such as the dynamics,bandwidth,and sensitivity of the entire system.This study designs a variable gain amplifier using the 0.18-μm bipolar process.The core structure of the circuit comprises a transconductance(GM)unit,GM unit biased module,and fixed gain amplifier.The fixed gain amplifier adopts a folded cascode structure to improve the gain and bandwidth.The design of the dB linear variable gain amplifier is realized by designing the GM unit bias circuit to generate continuous control current.The post-simulation results show that the power supply voltage is 5 V,the 3 dB bandwidth is 500 M Hz,the gain linear control range is within the range of-7.5-42.5 dB,and the output 1 dB compression point at half gain is 9 dBm.When the amplifier operates at 100 MHz,the control gain moves from minimum to maximum and the gain error is less than 1.3 dB under temperature conditions.
variable gain amplifierdB linear variable gainbipolar process
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