Patent ID: 7983625
Filing Date: 2011-07-19
Classification: H03H

Abstract:
1. A notch filter comprising: an input/output terminal; first and second variable capacitor circuits coupled to the input/output terminal, and having an intermediate node; a variable gain transconductance amplifier having an input coupled to the intermediate node, and an output; a peak detector having an input coupled to the output of the transconductance amplifier, and an output; a first comparator having a first input coupled to the output of the peak detector, a second input for receiving a reference voltage, and an output; a second comparator having a first input coupled to the output of the transconductance amplifier, a second input for receiving a reference frequency, and an output; and a control circuit having inputs coupled to the output of the first comparator and the second comparator, and outputs for controlling the first and second variable capacitor circuits and the transconductance amplifier.