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We report a novel PIN diode SiGe HBT variable gain amplifier (VGA) suited for the standard of WCDMA. The PIN diode which is employed in the feedback loop of the VGA play as a variable resistor to realize the gain control function. By adjusting the bias of the diode, the gain of the VGA can be changed. An inductor is utilized in the feedback loop to reduce the noise figure of the circuit. After matching the circuit, we get a variable gain amplifier with 21dB dynamic range, about 19dB maximum gain, and 2.6dB minimum noise figure. This work demonstrates a new method controlling the gain by adding a PIN diode in the feedback loop except changing the bias of the transistor.

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A UWB LNA (low noise amplifier) based on 0.35Jlm SiGe BiCMOS technology is presented in this paper. This LNA adopts a resistance feedback topology to optimize the gain and noise figure. The serial inductance at the base is used to matching input impedance and decreasing group delay variation. The simulation results indicate that the gain of LNA reaches 12.5dB with the variation of 1.9dB and the power consuming is 6.3mW in full band from 3.lGHz to 10.6GHz. This SiGe UWB LNA exhibits less than 5ps group delay variation and less than 3.85dB NF over the entire band.