Patent ID: 6995606
Filing Date: 2006-02-07
Classification: H03H

Abstract:
1. A high pass filter circuit, comprising: first and second input terminals at which a differential input voltage is applied; first and second output terminals at which a differential output voltage is provided; a first high pass filter portion coupled between the first input terminal and the first output terminal, including a first capacitor having first and second terminals, the first terminal of the first capacitor coupled to the first input terminal, and a first IGFET device having a source, a drain, and a gate, the drain of the first IGFET device coupled to the second terminal of the first capacitor and the source of the first IGFET device coupled to a bias voltage; a second high pass filter portion coupled between the second input terminal and the second output terminal, including a second capacitor having first and second terminals, the first terminal of the second capacitor coupled to the second input terminal, and a second IGFET device having a source, a drain, and a gate, the drain of the second IGFET device coupled to the second terminal of the second capacitor and the source of the second IGFET device coupled to the bias voltage; and a feedback circuit having a feedback circuit input terminal coupled to the first and second output terminals and having a feedback circuit output terminal coupled to the gate of the first IGFET and coupled to the gate of the second IGFET, wherein the feedback circuit is adapted to control a cutoff frequency of the high pass filter circuit.