The Design Of A BiCMOS Wide Gain Range Variable Gain Amplifier

The variable gain amplifier has been widely used in ultrasonic, laser radar, GPS, wireless communication and so on. As the key module in receivers, it adjusts the signals and makes sure that they can be given out in the same magnitude. With the development of the communication technology, the VGA is developing for higher dynamic range, linearity and better sensitivity. It's always a hotspot to research them.In this thesis, a VGA with higher dynamic range and linearity rely on a image demodulation chip is proposed. It is based on UMC 0.5um BiCMOS technology. By the principle that the gate voltage can change the effective resistance of the MOSFET, we structure the circuit, make the transconductance and effective load be controlled at the same time, instead of controlling them respectively, so that we can get higher gain range under the same control voltage. The core module is made up of three amplifiers which has the variable gain each; the regulator n. provides the calm working voltage for stabilization; the gain controlling module generates two asynchronism control voltages to ralize the delay control by using the current-compensate technology, in order to get the good noise figure and the control flexibility. The whole circuit has good robustness, meet the requirement in low power issipation, gain range, bandwidth and has good linearity. Compare with some other kinds of VGAs, this one is also competent.This thesis firstly introduces the background and application of the AGC, then describes the principle of the VGAs, the primary method to change the gain and the basic design request. Secondly, according to the chip criterion, the paper designs and emulates the sub-circuits in detail. At last, introduces the BiCMOS technology and the layout based on Cadence Virtuoso tool, which pass the DRC and LVS verification.This design belongs to the project"the research of the image demodulation chip in some wireless receiver"which is aimed at growing man with venturesome and innovative qualities in Suzhou. Because of its competent performance, it will be suited in other occasion if needed.