Help with bandgap reference

[gsuarez]

The circuit has the following parameters:
Check the circuit www.ece.uprm.edu/~s988025/pub/bandgap.png
Is=10^-15 A
dVbe/dT = -2.2mv/C

Temperature coefficient of 1500ppm/C
Voltage Coefficient of 100ppm/C

I'm not sure what is the relationship between the output voltage (Vref) and the temperature coefficient and the voltage coefficient. I know that Vref = Vout and can be found by Iref*R2+Veb4.

Since Veb4 is Vt*ln(Iref/Is) = (kT/q)*ln(Iref/Is) I can determine this amount for a particular temperature, but where does the temperature and voltage coefficient fit into all this?

 

[satyasiva]

just read bandgap reference chapter in Razavi's "design of analog ic's" book. u will get a good idea.

 

[rfzheng]

''Vref = Vout and can be found by Iref*R2+Veb4. ''
the formula that you have listed is just a one order temperature compensation. the Vref will be influenced by higher order temperature. so there are many paper concerned about higher order curvature compensation to reduce the temperature influence.

so you will have temperature co-efficient.
at the same time ,supply voltage will also infulence your reference voltage ,which is voltage coefficient.

but if your reference wroks in the normal state,both coefficient will not be so big as you listed