Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
1999-10-02
2001-09-04
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
C327S542000, C323S314000, C323S315000
Reexamination Certificate
active
06285244
ABSTRACT:
TECHNICAL FIELD
The present invention is generally related to integrated circuits, and more particularly to cross-coupled bandgap circuits and voltage reference circuits.
BACKGROUND OF THE INVENTION
In electrical circuits, and particularly integrated circuits (ICs), there is often a need to provide stable reference voltages and reference currents for use throughout the IC. These reference circuits attempt to provide stable and known voltages that vary little over time and temperature variations.
One such type of reference circuit is known as a cross-coupled bandgap circuit. Cross-coupled bandgap circuits are often used in operational amplifiers, voltage regulators, phase locked loops (PLLs), and other devices requiring a VCC insensitive reference generator.
Problems with many conventional cross-coupled bandgap circuits include that they are often times sensitive to low frequency noise on the VCC line, are temperature unstable, have varying reference voltages as the VCC varies between a low and high operating voltage.
There is desired an improved reference circuit, such as a cross-coupled bandgap circuit, that is temperature stable, VCC insensitive, and minimally effected by VCC sources having noise or voltage spikes thereon.
SUMMARY OF THE INVENTION
The present invention achieve technical advantages as a cross-coupled bandgap circuit having a current generator comprised of cross-coupled transistors being driven by a current mirror which operates to provide a stable voltage reference by canceling out the effects of varying temperatures during operation, as well as varying supply voltages and noise on the voltage source.
The present invention comprises a circuit providing a reference voltage to an output, comprising a current generator having a drive node and comprised of cross-coupled transistors. The current generator generates a first current. A current mirror is drivingly coupled to the current generator drive node and generates a second current mirrored to the first current. A reference current generator is also mirrored to this second current, this reference current generating the reference voltage. Preferably, this reference current is generated by a resistor and diode in series and tied to ground. The current mirror driving the cross-coupled transistors preferably comprises a multi-collector—PNP-Wilson current mirror. Further provided is a current sink circuit receiving the mirrored second current from the Wilson current mirror for sinking the second current to ground. This current sink preferably comprises 2 diodes, but their sizes do not require them to match the current generator sizes, and preferably comprises of serially connected diodes formed from bi-polar junction transistors (BJTs) with the respective collectors tied to the base.
The cross-coupled bandgap circuit is fabricated on a common die, wherein the pair of transistors forming the Wilson current mirror have approximately the same die area as at least three of the transistors forming the cross-coupled current generator.
The Wilson current mirror preferably comprises of at least one transistor having multiple collectors, with a first collector coupled to and driving the drive node of the cross-coupled current source, and a second collector being coupled to the reference current generator. The second current from the second collector of the Wilson current mirror is conducted through the current sink to ground, preferably through the two diodes which essentially establish approximately a 1.2 reference voltage at the emitter of the Wilson current mirror and also at the drive node of the cross-coupled current generator. The voltage reference is provided as an output of one of the multiple collectors of the Wilson current mirror, and is established by conducting the mirrored second current through a resistor and a diode serially connected to ground.
REFERENCES:
patent: 4816742 (1989-03-01), Van De Plassche
patent: 4958122 (1990-09-01), Main
patent: 5576616 (1996-11-01), Ridgers
patent: 6002293 (1999-12-01), Brokaw
Brady III Wade James
Callahan Timothy P.
Englund Terry L.
Stewart Alan K.
Telecky , Jr. Frederick J.
LandOfFree
Low voltage, VCC incentive, low temperature co-efficient,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Low voltage, VCC incentive, low temperature co-efficient,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low voltage, VCC incentive, low temperature co-efficient,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2458395