Apple Inc.
Bandgap circuit with beta spread reduction

Abstract:

A bandgap circuit is disclosed. The bandgap circuit includes a current source configured to generate, using a bias voltage, a first current and a second current, a first bipolar device configured to sink the first current, and a second bipolar device configured to sink the second current via a bias resistor. The bandgap circuit further includes an amplifier circuit configured to generate the bias voltage using a first voltage drop across the first bipolar device and a second voltage drop across the series combination of the bias resistor and the second bipolar device. A compensation circuit is also included, where the compensation circuit is configured to adjust, based on a value of the bias resistor, a base current of the second bipolar device.