how to form negative feedback in the PTAT?

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nksunmoon

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Can anybody help me?
how to connect the "+ -" input of the opa to form negative feedback in the PTAT circuit?
 

Hi,
can you elaborate you question in more detail if possible ? then I can try to suggest you something.
 

as we know, there is a opa in the PTAT circuit.And the opa has a positive input and a negative input, we should form negative feedback to make the two input terminal have the same voltage.Usually, one of the two inputs of the opa is connected to the triode branch,and the other one is connected to the branch which conclude a resistor and several triodes.So i am not very clear which input of the opa should be connected to the branch that conclude resistor and triodes.
is my question clear enough? Thank you for your helping!
 


whatever i understood from your description . to implement PTAT reference,there are two possible ways first with Vt reference PTAT generation with MOS and second if you want to implement it with diode or bipolar transistor then it is like Vbe PTAT reference in it there must be current mirror with two BJT and three resistor and one op amp . you are using opamp to make sure that both arm should have same voltage and maintain same potential across both arm.

i hope you will understand my point,
 

Read the the book "Design of Analog CMOS Integrated Circuits " by Razavi under Bandgap References.

It discusses about the feedback polarity.
 

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