Patent ID: 7429889
Filing Date: 2008-09-30
Classification: H03H

Abstract:
1. A control system for a fully programmable high precision filter having a filter input and a filter output including a first first-order low pass filter section comprising first and second mutually identical operational transconductance amplifiers (OTAs), each having a differential voltage input with first and second differential voltage input terminals and a single current output carrying a single phase current output signal, the first and second OTAs each having a controllable transconductance Gm from the differential voltage input to the single current output and being provided with first and second control inputs, respectively, the filter input being coupled to the first differential voltage input terminal of the first OTA, the current outputs of both first and second OTAs being resistorless coupled to a first capacitor, the current output of the second OTA being negatively fed back to its first differential voltage input terminal to form a variable positive virtual resistance across the first capacitor, the common connection of the single current outputs of the first and second OTAs and the first capacitor constituting an output terminal of the first first-order low pass filter section, which is coupled to the filter output, the second differential voltage input terminals of the first and second OTAs being respectively coupled to first and second DC reference voltage levels, comprising: a control signal device that is configured to receive an input gain control signal and a bandwidth control signal and includes a first multiplier that is configured to multiply the input gain control signal with the bandwidth control signal to provide an output gain control signal, and wherein: the output gain control signal is coupled to the first control input, and the bandwidth control signal is coupled to the second control input.