Bandgap reference circuit with a pre-regulator

Details Bandgap reference circuit with a pre-regulator Bandgap reference circuit with a pre-regulator

2001-11-20

2003-04-01

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

C327S513000, C323S314000

Reexamination Certificate

active

06542027

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
This invention relates in general to bandgap reference circuits and, more specifically, to devices and methods for providing bandgap reference circuits with low temperature coefficients.
BACKGROUND OF THE INVENTION
As shown in
FIG. 1
, a conventional bandgap reference circuit
10
includes a pre-regulator
12
that generates a regulated voltage V
REG
off the supply voltage V
CC
using a pair of current-mirror transistors Q
1
and Q
2
, a resistor R
1
, and a set of series-connected diodes D
1
, D
2
, and D
3
. In addition, a start-up circuit
14
—consisting of a bias transistor Q
3
, another set of series-connected diodes D
4
and D
5
, and a resistor R
2
—biases a pair of V
BE
-differential transistors Q
4
and Q
5
at start-up, after which the transistor Q
3
shuts off, thereby effectively isolating the start-up circuit
14
from the rest of the bandgap reference circuit
10
.
Together, a current source transistor Q
9
and a V
BE
-differential circuit
16
generate a differential voltage V
DIF
having a positive temperature coefficient from the regulated voltage V
REG
using a pair of current-mirror transistors Q
6
and Q
7
, the V
BE
-differential transistors Q
4
and Q
5
, a pair of resistors R
3
and R
4
, and a driver transistor Q
8
. As a result, the bandgap voltage V
BG
output from the bandgap reference circuit
10
across a resistor R
5
equals the differential voltage V
DIF
plus the base-emitter voltage V
BE
of the transistor Q
5
. Because the base-emitter voltage V
BE
has a negative temperature coefficient, any variations in the base-emitter voltage V
BE
due to temperature are countered by variations in the differential voltage V
DIF
, so that the bandgap voltage V
BG
should be relatively temperature independent. Unfortunately, the negative temperature dependence of the diodes D
1
, D
2
, and D
3
makes the regulated voltage V
REG
relatively temperature dependent, which, in turn, makes the bandgap voltage V
BG
relatively temperature dependent.
Accordingly, there is a need in the art for an improved bandgap reference circuit that has a low temperature coefficient.
SUMMARY OF THE INVENTION
In accordance with this invention, a pre-regulator for generating a regulated voltage for use in generating a bandgap voltage from a bandgap reference circuit includes a current source (e.g., a wilson current source) and a V
BE
multiplier that receives current therefrom and generates/clamps the regulated voltage. Also, feedback circuitry regulates the current flow from the current source in response to feedback from the bandgap voltage.
In other embodiments of this invention, the pre-regulator described above is incorporated into a bandgap reference circuit.
In still another embodiment of this invention, a reference voltage is generated by driving a current into a V
BE
multiplier to generate and clamp a regulated voltage. The current is regulated in response to feedback from the reference voltage. Also, a V
BE
differential voltage is generated from the regulated voltage using a V
BE
differential circuit, and the reference voltage is generated from the V
BE
differential voltage and a base-emitter voltage drop.


REFERENCES:
patent: 4749889 (1988-06-01), Lagoni et al.
patent: 5576616 (1996-11-01), Ridgers
patent: 5631551 (1997-05-01), Scaccianoce et al.
patent: 5686823 (1997-11-01), Rapp
patent: 5920184 (1999-07-01), Kadanka
patent: 5936392 (1999-08-01), Taylor
patent: 5952873 (1999-09-01), Rincon-Mora
patent: 6023185 (2000-02-01), Galipeau et al.
patent: 6114897 (2000-09-01), Ham
patent: 6411154 (2002-06-01), Mikulenka

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