Linear variable gain amplifier

Abstract

The invention discloses a linear variable gain amplifier. The linear variable gain amplifier comprises a gain gear selection unit, a current gain fine-tuning unit, an output unit, and a control unit, the gain gear selection unit receives differential signals output by a pre-stage and realizes different current gains according to the signal amplitude and the gain requirement, the current gain fine-tuning unit performs fine-tuning on the current gains and performs attenuation at a currently selected gain gear, the attenuation range is continuous and adjustable, and the output unit converts an output current after gain adjustment to a voltage and stably outputs a common-mode level of signals through a common-mode voltage feedback technology. According to the linear variable gain amplifier, continuous and linear adjustment of gains is realized, the gain adjusting range is wide, the gain control is accurate, the signal dynamic range is large, the output common-mode level is stable, the gain linearity is good, the gain temperature stability is good, the linear variable gain amplifier is used for conditioning input signals of an oscilloscope, and appropriate gains can be set according to vertical gears.

Description

technical field [0001] The invention relates to a linear variable gain amplifier. Background technique [0002] The variable gain amplifier is the most important component in the analog channel of the oscilloscope, which basically determines most of the analog performance in the analog channel of the oscilloscope, including key indicators such as vertical sensitivity, bandwidth, noise, and temperature drift. By changing the gain of the variable gain amplifier, the vertical sensitivity of the oscilloscope can be flexibly adjusted to expand the vertical dynamic range of the oscilloscope. [0003] refer to figure 1 , a typical oscilloscope 100 includes a signal input terminal 101, a high-resistance attenuation network 102, an AC-DC coupling circuit 103, a unity gain buffer circuit 104, a vertical offset circuit 105, a variable gain amplifier circuit 106, a bandwidth limiting circuit 107, an analog-to-digital conversion circuit (ADC) 108, control processing unit 109, and the l...

AI Technical Summary

Problems solved by technology

At present, the minimum resistance of most digital potentiometers on the market exceeds 30Ω, and the smaller the resistance, the greater the error, and it is difficult to achieve a small gain

Although this circuit can theoretically achieve a continuous adjustable current gain of 0 to 1, it is limited by the accuracy and adjustable range of the digital potentiometer in practical applications. It is already very good to reach 0.1 to 0.9, and the adjustable range of gain narrow

Moreover, the cost of digital potentiometers is relatively high, which is not suitable for cost-sensitive applications

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