Amplifier with band-pass filtering function

Abstract

The invention discloses an amplifier with band-pass filtering function, which comprises a variable gain amplifier, wherein the output end of the variable gain amplifier is connected with the input end of the variable gain amplifier through a Gm-C low-pass filter, which forms a feedback loop, so that the band-pass filtering function of the variable gain amplifier is realized. The input signal and the output signal of the variable gain amplifier are both differential signal, and the structure of the variable gain amplifier comprises ten MOS tubes, so that the amplifier has the advantages of simple circuit structure, small domain area and easy realization, and can effectively eliminate the influence of DC maladjustment of the low-frequency noise.

Description

technical field [0001] The invention relates to a variable gain amplifier, in particular to an amplifier with band-pass filter function. Background technique [0002] The superheterodyne receiver is a widely used system structure. Its basic principle is to amplify and down-convert the high-frequency signal received by the antenna into a fixed intermediate frequency signal. The intermediate frequency signal is adjusted to a suitable frequency by a variable gain amplifier. Amplitude, and then band-pass filtering to extract useful signals into demodulation. Among them, the existing band-pass filter circuit design is generally more complicated, taking the Gm-C band-pass filter as an example, such as figure 1 As shown, its circuit structure includes four Gm, respectively: Gm1, Gm2, Gm3, Gm4, wherein, the positive input terminal of Gm4 is connected to the positive input voltage Vinp, the negative input terminal is grounded, the positive input terminal of Gm3 is grounded, and the ...

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Problems solved by technology

Among them, the existing band-pass filter circuit design is generally more complicated, taking the Gm-C band-pass filter as an example, such as figure 1 As shown, its circuit structure includes four Gm, respectively: Gm1, Gm2, Gm3, Gm4, wherein, the positive input terminal of Gm4 is connected to the positive input voltage Vinp, the negative input terminal is grounded, the positive input terminal of Gm3 is grounded, and the negative input terminal Connect the negative input voltage Vinn, the output terminals of Gm4 and Gm3 are connected at Vout point, on the one hand, connect to the ground through the capacitor C1, on the other hand, connect the positive input terminal of Gm1 and the output terminal of Gm2, the negative input terminal of Gm1 and the positive input terminal of Gm2 respectively Grounded respectively, the output terminal of Gm1 and the negative input terminal of Gm2 are connected at the VLP point and grounded through the capacitor C2

Although this circuit has great advantages in filtering performance and Q value adjustment range, it also increases the circuit area and complexity.

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