Voltage or Current References Requirements of a Reference Circuit: Should be independent of power...
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![Page 1: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/1.jpg)
Voltage or Current References
Requirements of a Reference Circuit: • Should be independent of power supply• Should be independent of temperature • Should be independent of processing variations• Should be independent of noise
![Page 2: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/2.jpg)
Voltage or Current References
Requirements of a Reference Circuit: • Should be independent of power supply• Should be independent of temperature • Should be independent of processing variations• Should be independent of noise
S = ( Vref / Vref ) / ( Vdd / Vdd )Vdd
Vref
Sensitivity:
![Page 3: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/3.jpg)
Voltage or Current References
Requirements of a Reference Circuit: • Should be independent of power supply• Should be independent of temperature • Should be independent of processing variations• Should be independent of noise
S = ( Vref / Vref ) / ( Vdd / Vdd )Vdd
Vref
Sensitivity:
If sensitivity = 1, then 10% change in Vdd results in a 10% in Vref
![Page 4: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/4.jpg)
Simple Bias Circuits
Vout
Vdd
GND
Typically usinga potentiometer
![Page 5: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/5.jpg)
Simple Bias Circuits
Vout
Vdd
GND
Typically usinga potentiometer
S = 1Vdd
Vref
![Page 6: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/6.jpg)
Simple Bias Circuits
Vout
Vdd
GND
Typically usinga potentiometer
GND
Vout
Vdd
Transistor-basedresistive divider
S = 1Vdd
Vref
![Page 7: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/7.jpg)
Simple Bias Circuits
Vout
Vdd
GND
Typically usinga potentiometer
GND
Vout
Vdd
Transistor-basedresistive divider
S = 1Vdd
Vref
If KN = KP and VTN = |VTP|
S = 1Vdd
Vref
![Page 8: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/8.jpg)
Simple Bias Circuits
Vout
Vdd
GND
Typically usinga potentiometer
Typically poor Power Supply Rejection (low PSRR)
GND
Vout
Vdd
Transistor-basedresistive divider
S = 1Vdd
Vref
If KN = KP and VTN = |VTP|
S = 1Vdd
Vref
![Page 9: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/9.jpg)
Bias Circuits involving Diodes
GND
Vout
R
Vdd
GND
Iout
Current Source
MOSFET Source
![Page 10: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/10.jpg)
Bias Circuits involving Diodes
GND
Vout
R
Vdd
GND
Iout
Current Source
MOSFET Source
GND
Vout
R
Vdd
BJT Source
![Page 11: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/11.jpg)
Bias Circuits involving Diodes
Significant Power Supply Rejection (higher PSRR)
GND
Vout
R
Vdd
GND
Iout
Current Source
MOSFET Source
GND
Vout
R
Vdd
BJT Source
![Page 12: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/12.jpg)
Output Voltage Sensitivity
GND
Vref
R
Vdd
BJT Source Small-Signal model:
R
Vref
1/gm
GND
Vdd
![Page 13: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/13.jpg)
Output Voltage Sensitivity
GND
Vref
R
Vdd
BJT Source Small-Signal model:
R
Vref
1/gm
GND
Vdd Vref = Vdd / (1 + gm R)
gm = (Vdd0 – Vref0)/ R UT
![Page 14: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/14.jpg)
Output Voltage Sensitivity
GND
Vref
R
Vdd
BJT Source Small-Signal model:
R
Vref
1/gm
GND
Vdd Vref = Vdd / (1 + gm R)
gm = (Vdd0 – Vref0)/ R UT
Vref (1 + (Vdd0 – Vref0)/ UT ) = Vdd
S = (Vref / Vdd) (Vdd0 / Vref0)
= (Vdd0/Vref0)/(1 + (Vdd0–Vref0)/UT )
Vdd
Vref
![Page 15: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/15.jpg)
Output Voltage Sensitivity
GND
Vref
R
Vdd
BJT SourceS = (Vref / Vdd) (Vdd0 / Vref0)
= (Vdd0/Vref0)/(1 + (Vdd0–Vref0)/UT )
Vdd
Vref
![Page 16: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/16.jpg)
Output Voltage Sensitivity
GND
Vref
R
Vdd
BJT SourceS = (Vref / Vdd) (Vdd0 / Vref0)
= (Vdd0/Vref0)/(1 + (Vdd0–Vref0)/UT )
Vdd
Vref
Vdd0–Vref0 >> UT
S = (Vdd0/ (Vdd0–Vref0)) (UT / Vref0) Vdd
Vref
![Page 17: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/17.jpg)
Output Voltage Sensitivity
GND
Vref
R
Vdd
BJT SourceS = (Vref / Vdd) (Vdd0 / Vref0)
= (Vdd0/Vref0)/(1 + (Vdd0–Vref0)/UT )
Vdd
Vref
Vdd0–Vref0 >> UT
S = (Vdd0/ (Vdd0–Vref0)) (UT / Vref0) Vdd
Vref
~1
![Page 18: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/18.jpg)
Output Voltage Sensitivity
GND
Vref
R
Vdd
BJT SourceS = (Vref / Vdd) (Vdd0 / Vref0)
= (Vdd0/Vref0)/(1 + (Vdd0–Vref0)/UT )
Vdd
Vref
Vdd0–Vref0 >> UT
S = (Vdd0/ (Vdd0–Vref0)) (UT / Vref0) Vdd
Vref
~1
With Vref0 ~ 0.65, S = 0.04Vdd
Vref
![Page 19: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/19.jpg)
Bias Circuits involving Diodes
Significant Power Supply Rejection (high PSRR)
GND
Vout
R
Vdd
GND
R1
R2
Allows wider variation of output voltage
![Page 20: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/20.jpg)
Breakdown Diode Reference
![Page 21: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/21.jpg)
Breakdown Diode Reference
![Page 22: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/22.jpg)
Breakdown Diode Reference
Big Issue: Very noisy output voltage
SVREFVDD
VREF
VDD
VDD
VREF
vref
vdd
VDD
VBV
rZ
rZ R
VDD
VBV
![Page 23: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/23.jpg)
Bootstrapped Reference
GND
Vout1
Vdd Vdd
M3
M4
GND
Vout2
M2
M1
Iref
AI = (W/L)1 / (W/L)2
R
![Page 24: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/24.jpg)
Bootstrapped Reference
GND
Vout1
Vdd Vdd
M3
M4
GND
Vout2
M2
M1
Iref
AI = (W/L)1 / (W/L)2
VR
![Page 25: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/25.jpg)
Bootstrapped Reference
GND
Vout1
Vdd Vdd
M3
M4
GND
Vout2
M2
M1
Iref
AI = (W/L)1 / (W/L)2
In subthreshold (or BJTs): V = UT ln(AI) = Iref R
Iref = UT ln(AI) / R V
R
![Page 26: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/26.jpg)
Bootstrapped Reference
GND
Vout1
Vdd Vdd
M3
M4
GND
Vout2
M2
M1
Vdd
Iref
Iref
GND
Iref
AI = (W/L)1 / (W/L)2
In subthreshold (or BJTs): V = UT ln(AI) = Iref R
Iref = UT ln(AI) / R V
R
![Page 27: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/27.jpg)
Bootstrapped Reference
![Page 28: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/28.jpg)
Bootstrapped Reference
![Page 29: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/29.jpg)
Bootstrapped Reference
Startup Circuit
![Page 30: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/30.jpg)
Bootstrapped Reference
![Page 31: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/31.jpg)
Bootstrapped Reference
![Page 32: Voltage or Current References Requirements of a Reference Circuit: Should be independent of power supply Should be independent of temperature Should be.](https://reader036.fdocuments.us/reader036/viewer/2022062804/56649d8e5503460f94a767f4/html5/thumbnails/32.jpg)
Bootstrapped Reference
Startup Circuit