| 摘要 |
A DC offset canceling circuit. The DC offset canceling circuit applied in a variable gain amplifier includes chopper circuits, a transconductance amplifier, and at least one internal capacitor. The transconductance amplifier and at least one capacitor function as a filter for canceling DC offset of the variable gain amplifier. A first chopper circuit is inserted between the output of the variable gain amplifier and the input of the transconductance amplifier. A second chopper circuit is inserted between the output of the transconductance amplifier and the capacitor. The DC offset and low frequency noise of the transconductance amplifier, the undesired signal, is translated up to a chopping frequency by chopper circuits. The chopping frequency is much higher than the desired signal bandwidth, and the amount of the undesired signal in the passband of the signal is thereby greatly reduced.
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