Ac-Coupled Amplifier With Charge Pump Feedback
Original Publication Date: 1983-Sep-01
Included in the Prior Art Database: 2005-Feb-07
The present amplifier uses a charge pump feedback to reduce the output offset error. Input signal E IN, which may be the signal derived from a magnetic head in a disk file, is applied differentially to differential amplifier 1 through biasing network 2. Differential output voltage E OUT of differential amplifier 1 drives charge pump 3 which generates an output current linearly dependent on E OUT. Capacitor 4 integrates this current. Offset control circuit 5 senses the voltage across capacitor 4 and injects an error current into amplifier 1. This error current creates an offset bias in amplifier 1 to reduce the offset error in output voltage E OUT. Using this technique, the output current of charge pump 3 can be made small to allow capacitor 4 to have a value compatible with hybrid packaging.