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Design >> Analog Design >> bandgap voltage reference stability
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Message started by hchanda on Apr 20^th, 2007, 8:16am

Title: bandgap voltage reference stability
Post by hchanda on Apr 20^th, 2007, 8:16am

Hi all,

I have a very fundamental question on bandgap voltage reference stability, I am currently designing the bandgap where in the feedback there is an op-amp. The op-am I have designed is a folded cascode amplifier. The question I have is if frequency compensation necessary. According to my analysis there is one pole at the output of the opamp and the one at the input of the opamp. The output of op-amp is connected to the gate of cascode devices. The cascode devices provide current to bipolar.

But I have also seen bandgaps designed my peers where they implemented the above same structure but used a two stage opamp with lead compesation within the opamp. still there are three poles and a zero. I am not able to understand how this loop can be stable?

Aslo a very basic question how one can find intutively poles and zeros in RC or any circuits. Provided an RC circuit I always use mathematical equation to find poles and zeros, but without deriving equations and all how can I intutively find poles and zeros?

I appreciate your answers.

c