Patent ID: 6784725
Filing Date: 2004-08-31
Classification: G05F

Abstract:
A switched capacitor current reference circuit for generating a substantially constant reference current, comprising:a first transistor having a collector connected to a first voltage and an emitter connected to a second voltage by way of first and second series connected resistors; a second transistor having a collector connected to the first voltage, an emitter connected to the second voltage by way of a third resistor, and a base connected to a base of the first transistor; an op amp having a positive input terminal connected to a node between the first and second resistors, a negative input terminal connected to a node between the emitter of the second transistor and the third resistor, and an output terminal; a third transistor having a first terminal connected to the output terminal of the op amp and a second terminal connected to a first node; a first switched capacitor circuit connected between the first node and the second voltage; a second switched capacitor circuit connected between the first node and the second voltage, wherein the second switched capacitor circuit is connected in parallel with the first switched capacitor circuit; and a feedback path connecting the first node to a second node between the bases of the first and second transistors, and wherein the reference current is provided at a third terminal of the third transistor.