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DC offset canceling circuit applied in a variable gain amplifier

a technology of offset canceling circuit and variable gain amplifier, which is applied in the direction of amplifier details, differential amplifier, amplifier with semiconductor device/discharge tube, etc., can solve the problems of increasing design complexity and cos

Inactive Publication Date: 2002-07-04
SILICON INTEGRATED SYST R O C
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Consequently, both the design complexity and cost are increased.
Consequently, both the design complexity and cost are increased.

Method used

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  • DC offset canceling circuit applied in a variable gain amplifier
  • DC offset canceling circuit applied in a variable gain amplifier
  • DC offset canceling circuit applied in a variable gain amplifier

Examples

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Embodiment Construction

[0016] FIG. 2 shows a DC offset canceling circuit 26 applied in a variable gain amplifier 25 according to the present invention. The variable gain amplifier 25 includes a first amplifier 21, a second amplifier 22, a plurality of switches 201-208, and a plurality of resistors. The DC offset canceling circuit 26 includes a transconductance amplifier 23 and at least one internal capacitor 24. The switches 201-204 are used to adjust the variable gain of the first amplifier 21. For example, if the switch 201 is closed, then the gain will be raised; and if the switch 202 is closed, then the gain will be reduced. The switches 205-208 are used to adjust the variable gain of the second amplifier 22. For example, if the switch 205 is closed, then the gain will be raised; and if the switch 207 is closed, then the gain will be reduced. The transconductance amplifier 23 is used to transform the output voltage of the second amplifier 22 to an output current based on a ratio. The output of the tra...

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PUM

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Abstract

The present invention discloses a DC offset canceling circuit applied in a variable gain amplifier. The DC offset canceling circuit comprises a transconductance amplifier and at least one internal capacitor to function as a filter. The input of the transconductance amplifier is electrically connected to the output of the variable gain amplifier, and the output of the transconductance amplifier and the at least one internal capacitor are electrically connected to the input of the variable gain amplifier to form a feedback loop. To cooperate with the function of the DC offset cancelation, the input stage of the variable gain amplifier comprises an auxiliary differential pair.

Description

[0001] 1. Field of the Invention[0002] The present invention relates to a DC offset canceling circuit applied in a variable gain amplifier, and particularly to a DC offset canceling circuit which uses internal capacitors inside an IC for generating a filtering function.[0003] 2. Description of Related Art[0004] Variable gain amplifiers (VGA), which amplify input signals to necessary voltage levels of a system in demodulation process, are largely used in home network transceivers which transmit signals via cables. When the variable gain amplifier is used, a differential input end of an internal operational amplifier has the problem of intrinsic offset, and the intrinsic offset is always in the range of several mV to tens of mV. For wireless or wire communication, the maximum gain of the variable gain amplification is up to tens of dB; therefore, the intrinsic offset after amplification will affect the recovery ability of the received signal the characteristics of parameters of a dyna...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H03F3/45
CPCH03F3/45188H03F3/45659
Inventor YAO, CHI-TAISHEN, WEI-CHENLIU, HUNG-CHIH
Owner SILICON INTEGRATED SYST R O C