Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
2002-01-24
2003-10-07
Nguyen, Long (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
C327S542000, C323S313000
Reexamination Certificate
active
06630859
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a circuit and a method for producing a very low voltage power supply utilizing the band gap technology.
More particularly this invention relates to a band gap circuit which can operate at a voltage as low as 1.2 volts using a low power process.
2. Description of Related Art
FIG. 1
illustrates a conventional current band gap reference circuit. Devices
120
,
130
and
140
are bipolar transistors with their bases and collectors shorted together. This results in the creation of PN diodes
120
,
130
,
140
whose N side is connected to ground
110
in FIG.
1
. There are three p-channel MOSFETs in FIG.
1
. They are devices
190
,
155
and
195
. The drains of these devices are connected to the supply voltage, VDD
100
. These devices are used as current sources and current mirrors. Devices
170
and
180
are n-channel MOSFETs. They are also used in the current reference and current mirror function of this circuit. Similarly, resistor R
1
150
is used to bias the current reference formed by devices
155
,
180
and
130
. Resistor R
2
160
is used to bias the voltage reference formed by devices
195
and
140
.
The voltage at node ‘A’
175
has to be larger than Vtn+Vbe where Vtn is the threshold of the NMOS (n-channel metal oxide field effect transistor)
170
in FIG.
1
and where Vbe is the base to emitter voltage drop of bipolar transistor connected as a diode
120
. In a low power semiconductor manufacturing process, Vtn+Vbe could be close to 1.6 volts at a low temperature condition. This higher voltage level makes this circuit unsuitable for the low voltage, low power applications of today.
U.S. Pat. No. 5,686,823 (Rapp) “Bandgap Voltage Reference Circuit” describes a circuit comprising a feedback controlled current mirror, a band gap voltage generator, and a voltage comparator. This bandgap voltage reference circuit generates a bandgap voltage reference and a current mirror reference while operating over a wide power supply voltage range and down to very low power supply voltage levels.
U.S. Pat. No. 6,075,407 (Doyle) “Low Power Digital CMOS Compatible Bandgap Reference” describes a band gap reference that is compatible with a low voltage CMOS process. It utilizes ratioed current mirrors to provide loop gain and to minimize the offset sensitivity of the loop amplifier.
U.S. Pat. No. 6,150,872 (McNeil et al.) “CMOS Bandgap Voltage Reference” shows a band gap voltage reference circuit for 0.35 micron, 3-volt CMOS technology. This circuit operates in an essentially temperature independent manner and having low supply voltages.
BRIEF SUMMARY OF THE INVENTION
It is the objective of this invention to provide a circuit and a method for producing a very low voltage power supply utilizing the band gap technology.
It is further an object of this invention to produce a band gap circuit which can operate at a voltage as low as 1.2 volts using a low power process.
The objects of this invention are achieved by a low voltage supply band gap circuit made up of a PN diode ‘A’ whose N side is connected to ground and whose P side is connected to the plus input of a differential voltage comparator, a PN diode ‘B’ whose N side is connected to ground and whose P side is connected to one node of a series resistor. The series resistor whose other node is connected to the minus input of a differential voltage comparator, differential voltage comparator, a resistor ‘C’ which is connected to the output of said differential voltage comparator and to the plus input of said differential voltage comparator, a resistor ‘D’ which is connected to the output of said differential voltage comparator and to the minus input of said differential voltage comparator.
The objects of this invention are further achieved by a a method of providing a low voltage supply band gap circuit made up of the steps of connecting a PN diode ‘A’ whose N side is connected to ground and whose P side is connected to the plus input of a differential voltage comparator, connecting a PN diode ‘B’ whose N side is connected to ground and whose P side is connected to one node of a series resistor, and connecting said series resistor whose other node is connected to the minus input of a differential voltage comparator. In addition, the method steps include connecting the differential voltage comparator, connecting a resistor ‘C’ which is connected to the output of the differential voltage comparator and to the plus input of the differential voltage comparator, and connecting a resistor ‘D’ which is connected to the output of the differential voltage comparator and to the minus input of the differential voltage comparator.
REFERENCES:
patent: 5568045 (1996-10-01), Koazechi
patent: 5686823 (1997-11-01), Rapp
patent: 5712590 (1998-01-01), Dries et al.
patent: 5867013 (1999-02-01), Yu
patent: 6075407 (2000-06-01), Doyle
patent: 6150872 (2000-11-01), McNeill et al.
patent: 6411158 (2002-06-01), Essig
Ackerman Stephen B.
Nguyen Long
Saile George O.
Taiwan Semiconductor Manufacturing Company
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