Patent ID: 6351111
Filing Date: 2002-02-26
Classification: G05F,Y10S

Abstract:
A current reference circuit for providing a current reference that has a controlled temperature coefficient and is relatively stable with supply voltage fluctuations, the current reference circuit having a reference leg and a mirror leg configured such that the current in the reference leg is mirrored in the mirror leg, wherein a resistor in the reference leg may be fabricated using standard processes and occupy minimum space, the current reference circuit comprising the following:A) a first voltage source, configured to supply a first voltage during operation; B) a second voltage source, configured to supply a second voltage during operation that is lower than the first voltage; C) a reference leg coupled between the high voltage source and the low voltage source, the reference leg comprising the following: i) a plurality of MOS transistors coupled in series between the high voltage source and the low voltage source, the plurality of MOS transistors comprising: a) a group of at least one PMOS transistor that is electrically closer in the series to the high voltage source; and b) a group of at least one NMOS transistor that is electrically closer in the series to the low voltage source; and ii) a series composite resistor comprising at least a first series resistor and a second series resistor that are coupled in series with each other between the high and low voltage sources, wherein the series composite resistor is disposed on either side of the plurality of MOS transistors in series between the high and low voltage sources, wherein the first series resistor and the second series resistor are fabricated differently; and D) a mirror leg coupled between the high voltage source and the low voltage source, the mirror leg coupled with the reference leg so that current flowing through the reference leg is mirrored in the mirror leg.