Adjustable gain amplifier

Abstract

The invention discloses an adjustable gain amplifier which comprises an input circuit, a high gain amplification circuit, a low gain amplification circuit, a load circuit, an output circuit and a gain adjusting circuit. The input circuit is connected with the high-gain amplification circuit and the low-gain amplification circuit; the load circuit is connected with the high-gain amplification circuit and the low-gain amplification circuit through the gain adjusting circuit. And the output circuit is connected with the load circuit. According to the invention, the total gain adjustment can be realized, and the amplification of the differential signal is not easy to distort.

Description

technical field [0001] The invention relates to the field of electronic circuits, in particular to an adjustable gain amplifier. Background technique [0002] In modern high-speed signal processing, an amplifier is often needed to amplify and transmit the signal, and the gain of the amplifier sometimes needs to be controllable and adjustable; The signal is saturated and distorted; or a specific amplification gain is set according to the application requirements, so an amplifier with adjustable gain is required. [0003] Currently commonly used gain-adjustable amplifiers such as figure 1 As shown, the total gain GA of the gain adjustable amplifier is: [0004] GA=G m *R; [0005] [0006] [0007] where G m is the equivalent transimpedance of the gain adjustable amplifier, R is the resistance value of the load resistor R, r s is the resistance value of the output pole resistor RS, μC ox is the physical parameter of the process device, W / L is the channel width-to-...

AI Technical Summary

Problems solved by technology

[0010] 1. Adjusting the resistance of the load resistor R and the output current of the tail current I will affect the static operating point of the circuit; for example, when the input signal is large, reducing the resistance of the load resistor R or the output current of the tail current I will make the gain The overall gain of the adjustable amplifier is reduced, but the swing space of the output signal is also reduced, which makes the output signal very likely to be severely distorted;

[0011] 2. Adjusting the resistance value of the output resistor RS or the output current of the tail current I will affect the characteristics of the amplifier tube, such as ft value / noise characteristics, etc., which are not suitable for application scenarios requiring low noise or stable bandwidth characteristics

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