Patent ID: 7038533

Claim:
An apparatus for providing an adjustable bandwidth high pass filter, the apparatus comprising: a high pass filter having an input capacitor coupled in series with a resistive ladder having a plurality of resistors coupled in series, the coupling between the capacitor and a first resistor of the resistive ladder defining a first tap and successive couplings between resistors forming successive taps, a last resistor of the resistive ladder being coupled to a ground; a plurality of bandwidth adjusting resistors, each having a first side coupled to the first tap; and a plurality of MOSFET devices, each MOSFET device having a source, a gate and a drain, the source of each MOSFET device coupled to a second side of one of a corresponding bandwidth adjusting resistor; the drain of each MOSFET device coupled to said ground and the gate being coupled to a corresponding control circuit, each control circuit comprising an amplifier output coupled to the gate of the corresponding MOSFET device, each amplifier comprising a tristate buffer amplifier and a pull-up resistance coupled between the output of the tristate buffer amplifier and a power supply.