aks
New Member
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Posts: 5
Bangalore
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Hi
Need some help in understanding Brokaw's bandgap cell. As far as my understanding in Bandgap circuit there are two feedbacks (+ve and -ve both) but -ve feedback should be the dominant in order to have stable circuit. But by looking at picture below (from brokaw's bandgap paper) it appears that loop formed by vout--> Q2--> -ve i/p of opamp to vout should be -ve feedback as it has larger feedback factor compared to the loop formed by vout--> Q1--> +ve i/p of opamp to vout. But loop formed by vout->Q2-->-ve i/p opamp->vout suggests it has 360 deg phase shift (base to collector of BJT 180 deg + Opamp =180deg). If so the how is this circuit stable and how does it correct itself to vout=Bandgap ref? Please enlighten me on this and correct me if I am missing any basic.
Thanks AKS
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