Bootstrap circuit to cancel input bias currents of a differential amplifier over most of common-mode input voltage range

摘要

An electronic circuit to cancel the input bias currents of a differential amplifier over most of the common-mode input voltage range is provided. The circuit includes an arrangement of transistors, current mirror and current sources to track the input bias currents of the differential amplifier even when the common-mode voltage is within at least 0.2 volts of the supply rail voltage level. The input bias cancellation currents are generated by tracking the input bias currents and injected into the differential amplifier inputs to cancel the input bias currents. The circuit includes a bootstrap loop to track the input bias currents when the common-mode voltage fluctuates.