A High Linearity Variable Gain Amplifier

Abstract

The invention discloses a high-linearity variable gain amplifier. The high-linearity variable gain amplifier comprises a variable gain amplifier capable of carrying out amplification or attenuation on a signal; the variable gain amplifier adopts a closed-loop negative feedback structure and also adopts an exponential gain control circuit for controlling voltage by generating gains, so that the gain of the variable gain amplifier is continuously changed in a dB linear manner; the variable gain amplifier is composed of a full differential operational amplifier, two input PMOS (P-channel Metal Oxide Semiconductor) tubes and two feedback PMOS tubes; the full differential operational amplifier adopts a two-grade structure, and a bias circuit and a common-mode feedback circuit are arranged; a common-source and common-gate compensation technology is adopted to obtain an enough phase margin, so that the stability of a feedback loop is guaranteed. The linearity is improved and the gains are continuously adjusted in an exponential manner.

Description

technical field [0001] The invention relates to the design of an integrated circuit, in particular to the design of a variable gain amplifier. Background technique [0002] In a wireless communication system, due to the channel fading phenomenon, the amplitude range of the receiver input signal varies greatly (up to dozens of dB). In order to reduce the bit error rate, the receiver is usually equipped with an automatic gain control circuit (Automatic Gain Control, AGC), and the variable gain amplifier is the main part of the AGC system. At present, the key points and difficulties of variable gain amplifier research are mainly reflected in: wide bandwidth, high gain dynamic range and high linearity. It is difficult for most designers to achieve high linearity in the range of wide bandwidth and high gain, and achieving high linearity may sacrifice bandwidth and gain. [0003] In the prior art, variable gain amplifiers are divided into two types: open loop and closed loop. T...

AI Technical Summary

Problems solved by technology

The open-loop variable gain amplifier can achieve continuously adjustable gain, but the stability is poor, the linearity is low, and the dynamic range of the signal is small; the closed-loop variable gain amplifier uses the form of negative feedback, and its performance is relatively stable. The gain depends on the ratio of the resistors, and the linearity is high, but it is difficult to realize the continuous adjustment of the gain

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