Method of curvature compensation, offset compensation, and capacitance trimming of a switched capacitor band gap reference

摘要

Curvature in a reference voltage produced by a switched capacitor band gap reference circuit is compensated by producing a first DELTA VBE voltage by causing first and second PTAT/R currents to flow through a first DELTA VBE-generating circuit. The first DELTA VBE voltage is applied to a first terminal of a first capacitor having a second terminal coupled to a summing conductor of an operational amplifier producing the reference voltage. A second DELTA VBE voltage is produced by causing a third PTAT/R current and a fourth current to flow through a second DELTA VBE-generating circuit. The second DELTA VBE voltage is applied to a first terminal or a second capacitor having a second terminal coupled to the summing conductor. First and second charges are transferred from the first and second capacitors through the summing conductor into a feedback capacitor coupled between the summing conductor and an output of the operational amplifier to produce the compensated reference voltage on the output of the operational amplifier. A technique of storing a voltage on the feedback capacitor equal to a VBE voltage minus a voltage on the summing conductor during a charging phase, and then connecting the feedback capacitor between the summing conductor and the output of the operational amplifier cancels the offset voltage of the amplifier.