Help!!!how to construct a PTAT bias current with using a ba?

[shuiyun]

How to construct a PTAT bias current ?You can only using the output of a bandgap,but you can't use any node inside the bandgap?

How to implement it ? I can't achieve this achieve by not using the bias current node of the bandgap amplifier?

 

[ambreesh]

Re: Help!!!how to construct a PTAT bias current with using a

I am sure we can do it. following are 2 options:
1. The BGR has a inbuilt PTAT current generation. ΔVbe is PTAT in nature.
The current flowing in BGR core is PTAT you could simply mirror it.
2.Kindly look at the file attached.
Make R1 as CTAT. And the CTAT tempco of the resistor is more than ctat tempco of the BGR voltage as temp increases.
We are asssuming that BGR output is PTAT below room temp and CTAT above room temp
If it is unclear you could get back