Abstract: The invention relates to a microprocessor-programmable, universal active filter. The filter has an input section, an operational amplifier with two input nodes, a bandpass section, a lowpass section and control circuitry which, under clock control, periodically brings one of the inputs of the operational amplifier to within a low, d.c. offset voltage, approaching zero volts, of the other input. The output of the lowpass filter section is coupled to the input of the bandpass filter section and the lowpass section also has a feedback loop back to the bandpass section. The selectivity "Q", the gain, center frequency and the output characteristics, such as bandpass, lowpass, allpass, highpass or notch, of the filter may be selected using MOS switches under microprocessor control.

Abstract: An electronic comparator circuit (10) adapted for implementation as an integrated circuit semiconductor device provides high resolution and high speed performance. The circuit comprises a first differential amplifier (12) with clamping diodes (50, 52) that allow a fast response; a source-follower stage (14) connected to the first differential amplifier for buffering its output to enable it to be broadbanded; a second differential amplifier (16) driven by the source-follower stage for handling large signal swings while providing additional gain, a level shift stage (18) for driving the output stage in a class A-B mode, and a cascode output stage (20) which provides increased circuit gain and an output signal which ranges from the positive supply voltage (V.sub.DD) to the negative supply voltage (V.sub.SS).