variable gain amplifier

Abstract

The present invention provides a variable gain amplifier, which includes: an operational amplifier; at least one series resistor circuit with one end as a signal input end and the other end connected to the output end of the operational amplifier, and a plurality of resistors connected in series; and A switch circuit connected to multiple nodes of each series resistor circuit and an input terminal of the operational amplifier is used to control the on-off of multiple nodes of each serial resistor circuit and an input terminal of the operational amplifier, so that each Part of the resistance in a series resistance circuit is used as the input resistance of the operational amplifier, and the rest of the resistance is used as the feedback resistance of the operational amplifier; and a decoding circuit is used to decode the input control signal and output it for controlling the operational amplifier. The opening and closing signals of the opening and closing of the plurality of controlled switches. The invention has the advantages of removing the switch circuit from the signal path, thereby eliminating the influence of the on-resistance of each switch on the input impedance and feedback impedance of the operational amplifier, and improving the linearity of the gain.

Description

technical field [0001] The invention relates to the field of circuits, in particular to a variable gain amplifier. Background technique [0002] In modern wireless communication technology, due to the uncertainty of received signal power, automatic gain control has become an important module in the communication system, and the variable gain amplifier is the core of the automatic gain control loop. The automatic gain control loop adjusts the gain control signal of the variable gain amplifier to stabilize the amplitude of the output signal within a range without being affected by the amplitude of the input signal, thereby reducing the difficulty of subsequent circuit processing signals. Linearity, low noise, low power consumption, high bandwidth, and a linear relationship with the gain control signal in dB are all basic requirements for a variable gain amplifier. [0003] The following are two commonly used gain variable amplifier structures: [0004] The first type: see f...

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Problems solved by technology

However, the variable gain amplifier used in this patent is an open-loop structure, so the linearity of the variable gain amplifier is low

[0009] On the other hand, since the on-resistance between the source and drain of the transistor is not completely linear with the gate voltage, although the achievable gain adjustment step interval is small, the step size is not constant and the deviation is large, so it cannot be adjusted in Accurate linear relationship in dB

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