bandgap reference circuit - alab.ee.nctu.edu.t · bandagap output voltage (v) temperature (o c) tt...

Nanoelectronics and Gigascale Systems Lab.奈米電子與晶片系統實驗室

1National Chiao Tung University國立交通大學

ICS Lab.

Bandgap reference circuit 307暑期訓練課程



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General Considerations

To generate a voltage or current reference that is independent of the supply voltage and process and has a well-defined behavior with temperature.

The required temperature dependence assumes one of three forms :• Proportional to absolute temperature (PTAT)• Constant-Gm behavior• Temperature independent



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General Considerations

The sensitivity of a parameter y to a second one x is defined as

The variation of a parameter y that results from changes in temperature is usually characterized by its fractional temperature coefficient, which is defined as the fractional change per degree centigrade change in temperature



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Simple Current Sources The output current of the circuit is quite sensitive to VDD



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Supply-Independent Biasing Supply-Independent Current Generator (ΔVGS reference)

Output current is determined by K and RS

The current is independent of the supply voltage, but still a function of process and temperature.



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Temperature independent References If a reference is temperature independent, then it is usually process-

independent as well. If two quantities having opposite temperature coefficients (TCs) are added

with proper weighting, the result displays a zero TC. To obtain a reference voltage with zero TC



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Temperature independent References The forward voltage of a PN-junction diode exhibits a negative TC.



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Temperature independent References PTAT Generator

If two identical transistors (IS1 = IS2) are biased at collector currents of nI0and I0 , and their base currents are negligible

Thus, VBE difference exhibits a positive temperature coefficient



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Bandgap reference example Kujik Bandgap reference

Vos is amplified by 1+R2/R3 Vos itself varies with temperature, raising the temperature coefficient of the

output voltage.



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Bandgap reference example



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Bandgap reference Output Issues



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Bandgap reference schematic

185

35

213

213

25

25

123

123

810

25

25

810

8 p

0.2210

0.55

100.5

0.845

0.845

119k119k

13k

65

65

2npn 2npn

10 p10M

Transistor level implementation of bandgap referenceThe gain-enhanced OPAMP



ICS Lab.




ICS Lab.


-40 -20 0 20 40 60 80 1001.215

1.220

1.225

1.230

1.235

1.240

1.245Ba

ndag

ap O

utpu

t Vol

tage

(V)

Temperature (oC)

TT FF SS



ICS Lab.

Bandgap reference Specs.

Parameter SpecificationTechnology CIC 0.18umSupply voltage 1.8vReference voltage 1.225v@27℃Static current Consumption 26.3uATC @ VDD=1.8v 25ppm/℃PSR @ 10kHz 90.3dB

bandgap reference circuit - alab.ee.nctu.edu.t · bandagap output voltage (v) temperature (o c) tt...

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