Why the output BGR voltage is a concave curve in my bandgap design?

[fuxinmingming]

Hi all,
i am designing a banba bandgap. However, the output BGR voltage is a concave curve. Can anyone explain why this happen?:|

 

[threekingtiger]

Re: Bandgap design

Hi, it seems to be abnormal because many books proposed convex V-temp curve. Even you can differentiate the expression of Vref(T) twice to find that the curve should be convex because Second Derivative of Vref(T) is negative.

As a matter of fact, the temperature coefficient of other passive components such as the resistors you choose may have some influence on Vref's TC characteristics. But your Vref(T) used to be differentiated might never contain any information on resistor's TC, right?

Sometimes the curve will be concave. So do not fuss it at all. HaHa~

 

[pankajdudulwar]

Bandgap design

please provide your bandgap circuit with the curve only guess can be made

 

[ammarzouk]

Re: Bandgap design

the plot alone is not enough. Could you upload the schematic? What kind of toplogy are you using?

 

[hackjiang]

Bandgap design

I can only have two guess:
1. Pay attention to the Resistor Temp coefficient, adjust the resistor value.
2. The bipolar model become less accurate at high temperature. It always happens to me. In your case,maybe the real measured curve will not like things you posted.