Gradient voltage generator used for continuous variable gain amplifier

Abstract

The invention relates to a gradient voltage generator used for a continuous variable gain amplifier, which comprises a forward output circuit, an inverted output circuit, a CMOS (Complementary Metal Oxide Semiconductor) transconductance circuit and a common-mode voltage generating circuit, wherein the CMOS transconductance circuit is used for converting the input voltage into current and transferring the current to the forward output circuit and the inverted output circuit through a current mirror which is formed by respectively connecting a drain electrode of a first NMOS (N-channel metal oxide semiconductor) pipe, a drain electrode of a second NMOS pipe, a drain electrode of a first PMOS pipe in the forward output circuit and a drain electrode of a second PMOS pipe in the inverted output circuit; and the input voltage of the common-mode voltage generating circuit and the common-mode voltage of the continuous variable gain amplifier are same, and the output ends of the common-mode voltage generating circuit are respectively connected with the low voltage input ends of both the forward output circuit and the inverted output circuit. By using the COMS transcomductance circuit of the invention, the relation between the gain characteristic curve of the continuous variable gain amplifier and the VAGC (Voltage Automatic Gain Control) is more accurate, and the influence of the process, the temperature, and the voltage to the performance of the continuous variable gain amplifier is decreased to be lowest.

Description

Technical field: [0001] The invention relates to a slope voltage generator for a continuously variable gain amplifier. Background technique: [0002] figure 1 It is the basic structure of a continuously variable gain amplifier (VGA), and its core circuit is two cascaded operational amplifiers (Opamp). Negative feedback resistors R1 and R2 determine the gain of the amplifier. The slope voltage generator (Ramp Gen) accepts the control voltage V from the automatic gain control circuit (AGC) AGC , and convert it into a set of control voltages and send them to the adjustable resistors R1 and R2, thereby realizing the gain control of the continuously variable gain amplifier (VGA). [0003] figure 1 In the VGA, its single-stage gain is equal to R2 / R1. As we all know, most RF receiving systems require VGA gain and control voltage (V AGC ) within a certain range into a "decibel-linear" relationship (such as figure 2 ). A common approximation method is to make R2 / R1=(1+X) / (1-...

AI Technical Summary

Problems solved by technology

[0006] To sum up, the gain and control voltage VGA of the VGA based on the traditional structure Ramp Gen circuit AGC The relationship is imprecise, susceptible to process, temperature, voltage changes, and for different common-mode voltages, the gain characteristic curve is different

These issues affect the performance of the VGA and reduce its usefulness

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