Bandgap reference circuit with offset voltage removal

摘要

An example bandgap reference circuit includes an amplifier, a first, a second, and a third switch, and a capacitor. The first switch is coupled between an inverting input and an output of the amplifier to provide a negative feedback loop around the amplifier when the first switch is closed. The capacitor has a first end coupled to the inverting input, and a second end coupled to the second switch, where the capacitor is charged to a voltage substantially equal to an offset voltage of the amplifier when the second switch is closed. The third switch is coupled to a second end of the capacitor, where the voltage across the capacitor is subtracted from an input loop of the reference circuit to cancel the offset voltage of the amplifier when the third switch is closed.

主权项

1. A bandgap reference circuit, comprising:
an operational transconductance amplifier (OTA) having an inverting input and a non-inverting input; a first switch coupled between the inverting input and an output of the OTA to provide a negative feedback loop around the OTA when the first switch is closed; a capacitor having a first end coupled to the inverting input, and a second end; a second switch coupled to the second end of the capacitor, wherein the capacitor is charged to a voltage substantially equal to an offset voltage of the OTA when the second switch is closed; a third switch coupled to the second end of the capacitor, wherein the voltage across the capacitor is subtracted from an input loop of the reference circuit to cancel the offset voltage of the OTA when the third switch is closed; a first bipolar transistor having a collector coupled to a first node between a first resistor and the third switch; and a second bipolar transistor having a collector coupled to a second node between a second resistor and the second switch, wherein the non-inverting input of the OTA is coupled to the second node, wherein the bandgap reference circuit is to be coupled to receive a first signal that synchronizes the readout of each row of a pixel array included in an imaging sensor, and wherein the bandgap reference circuit is configured to refresh the voltage reference during the readout of each row of the pixel array in response to the first signal.