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REFERENCE CIRCUITS
What is a Reference Circuit?
A reference circuit is an independent voltage or current source which has
a high degree of precision and stability
Requirements for a Reference Circuit:
1.)Output voltage/current should be independent of power supply.
2.)Output voltage/current should be independent of temperature.
3.)Output voltage/current should be independent of processing variations
V-I Characteristics of an Ideal Reference
i
Voltage Reference
Iref
Current Reference
Vref
v
Concept of Sensitivity
Definition
Sensitivity (S) is a measure of dependence of Vref (Iref) upon a
parameter or variable x which influences Vref (Iref).
For example, if the sensitivity is 1, then a 10% change in x
will cause a 10% change in Vref.
Ideally, SVREFX(VDD,Temp)0
Types of references
1. Voltage dividers - passive and active.
2. MOS diode reference.
3. PN junction diode reference.
4. Gate-source threshold referenced circuit.
5. Base-emitter referenced circuit.
Targil Kita.
Estimate accuracy and sensitivity to power for the
following Passive & Active Voltage References
PN_Junction Voltage reference and MOS
Equivalent (Gate source)
Targil Kita II.
What is the Voltage Reference of the PN junction and
MOS equivalent circuits?
How can we modify these Voltages?
Bootstrapped Current Source
Vgs?, Iout?