[SOLVED] Bandgap voltage variation with load

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xplorin

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Hi,

I am trying to design a bandgap circuit. For small loads, my bandgap circuit is working fine over all corners and the bandgap voltage remains the same.
With small loads the bandgap variation with temperature is only 5mV i.e., vbg ranges from 734.5mV to 739.8mV. As the load is increased, bandgap voltage drops by a large amount and there is a huge variation in the bandgap voltage with temperature. is this because of any leakage from gate to body or Something?........kindly help me to sort out this issue.

The plots are given inthe attachments





Thanks & Regards
 

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  • bandgap_ckt.png
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  • low-load.png
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Hello xplorin

The bandgap reference voltage is not designed for driving high loads, and this is the basic difference between the voltage reference and the voltage source.
therefore you should take the voltage from the bandgap reference without loading it. if you have a resistive load then use op-amp buffer between them.

the reason behinf that the reference voltage will not work properly at higher load is that the current will be decided between the load and the bipolar transistor . any change in that current will change the setting of the circuit and the balance that you already achieved.
 
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