Bandgap Voltage Reference
Bandgap Voltage Reference
Bandgap Voltage Reference
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A bandgap voltage reference is a temperature independent voltage reference circuit widely used in integrated
circuits. It produces a xed (constant) voltage regardless
of power supply variations, temperature changes and circuit loading from a device. It commonly has an output
voltage around 1.25 V (close to the theoretical 1.22 eV
bandgap of silicon at 0 K). This circuit concept was rst
published by David Hilbiber in 1964.[1] Bob Widlar,[2]
Paul Brokaw[3] and others[4] followed up with other commercially successful versions.
I C in mA
1,5
1,0
0,6 mA
UBE1 +UBE
UBE2
0,5
0,55
0,60
0,65
0,70
0,75
0,80
0,85
0,90
U ref in V
Operation
R1
R2
+
I C1
10E
I C2
T1
UBE1
R3
UBE
R4
UTemp
Uref
T2
UBE2
Note that sometimes confusion arises when using the abbreviation CTAT, where the C is incorrectly taken to
The voltage dierence between two p-n junctions (e.g. mean "constant rather than "complementary. To avoid
diodes), operated at dierent current densities, is used to this confusion, although not in widespread use, the term
generate a proportional to absolute temperature (PTAT) constant with temperature (CWT) is sometimes used.
current in a rst resistor. This current is used to generate a When summing a PTAT (Proportional to Absolute Temvoltage in a second resistor. This voltage in turn is added perature) and a CTAT (Complementary to Absolute
to the voltage of one of the junctions (or a third one, in Temperature) current, only the linear terms of current
some implementations). The voltage across a diode op- are compensated, while the higher-order terms are limerated at constant current, or here with a PTAT current, iting the TD (Temperature Drift) of the BGR at around
is complementary to absolute temperature, with approx- 20ppm/o C, over a temperature range of 100 o C. For this
imately 2 mV/K. If the ratio between the rst and sec- reason, in 2001, Malcovati [5] designed a circuit topolond resistor is chosen properly, the rst order eects of ogy that can compensate high-order non-linearities, thus
the temperature dependency of the diode and the PTAT achieving an improved TD. This design used an improved
current will cancel out. The resulting voltage is about 1.2 version of Banba [4] topology and an analysis of base1.3 V, depending on the particular technology and circuit emitter temperature eects that was performed by TsiCircuit of a Brokaw bandgap reference
vidis in 1980.[6] In 2012, Andreou [7] [8] has further improved the high-order non-linear compensation by using
a second opamp along with an additional resistor leg at
the point where the two currents are summed up. This
method enhanced further the curvature correction and
achieved superior TD performance over a wider temperature range. In addition it achieved improved line regulation and lower noise.
The other critical issue in design of bandgap references is
power eciency and size of circuit. As a bandgap reference is generally based on BJT devices and resistors, the
total size of circuit could be large and therefore expensive for IC design. Moreover, this type of circuit might
consume a lot of power to reach to the desired noise and
precision specication.[9]
Patents
1966, US Patent 3271660, Reference voltage source,
David Hilbiber.[10]
1971, US Patent 3617859, Electrical regulator apparatus including a zero temperature coecient voltage
reference circuit, Robert Dobkin and Robert Widlar.[11]
1981, US Patent 4249122, Temperature compensated bandgap IC voltage references, Robert Widlar.[12]
1984, US Patent 4447784, Temperature compensated bandgap voltage reference circuit, Robert
Dobkin.[13]
See also
Brokaw bandgap reference
LM317
Silicon bandgap temperature sensor
References
[1] Hilbiber, D.F. (1964), A new semiconductor voltage standard, 1964 International Solid-State Circuits
Conference: Digest of Technical Papers 2: 3233,
doi:10.1109/ISSCC.1964.1157541
[2] Widlar, Robert J. (February 1971), New Developments
in IC Voltage Regulators, IEEE Journal of Solid-State Circuits 6 (1): 27, doi:10.1109/JSSC.1971.1050151
[3] Brokaw, Paul (December 1974), A simple three-terminal
IC bandgap reference, IEEE Journal of Solid-State Circuits 9 (6): 388393, doi:10.1109/JSSC.1974.1050532
EXTERNAL LINKS
5 External links
The Design of Band-Gap Reference Circuits: Trials and Tribulations p.286 Robert Pease, National
Semiconductor
Features and Limitations of CMOS Voltage References
ECE 327: LM317 Bandgap Voltage Reference
Example Brief explanation of the temperatureindependent bandgap reference circuit within the
LM317.
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