Patent ID: 7639081
Filing Date: 2009-12-29
Classification: G05F,H03F

Abstract:
1. A circuit, comprising: an input node and an output node; a compound cascode current mirror (CCCM) with an input leg and an output leg, and each leg comprises a mirror transistor connected in series with its cascode transistor with a connection node between a drain of the mirror transistor and a source of the cascode transistor; each cascode transistor of the input leg and output leg having a drain terminal which is connected to the input node and output node, respectively; the input node is further connected to gate terminals of the mirror transistors; and the connection node of the input leg is maintained at a voltage that is an overdrive voltage of the mirror transistor of the input leg; the gate terminal of each cascode transistor of the input leg and output leg is driven at a control voltage; the control voltage and the overdrive voltage are both part of a feedback loop which maintains the overdrive voltage; wherein the feedback loop comprises an amplifier driving the control voltage at an output node of the amplifier, receives the overdrive voltage at an input node of the amplifier, and reproduces the overdrive voltage at a feedback node of the amplifier; and the output node of the amplifier is connected to the gate terminals of the cascode transistors and the feedback node is connected to the connection node of the input leg of the CCCM.