Need help...A Simple bandgap reference.

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hipichu777

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Hello every one, i'm new here and new to analog IC design.

Here's my first real job.

I need to design a bandgap reference (with startup) whose output is around 1.8v and is independent of temperature (-40 to 105 c) and vdd (2.7 to 3.3v)
using opamp and 8:1 BJT pairs in smic18 and Cadence environmnet.

Circuits shown below.

I know it's not that difficult, but i have been trying this for over a week and has got very limited results (output change greatly over variation of vdd)

Could anyone show me a real circuit that could work that way?

Thank you very much indeed.
 

It is a self-biased bandgap.
However, I suggest changing start-up circuit with detecting scheme.
 

Thanks for the advice, but right now I just want to make this work, and then improve it with other structure.
 

1) the third terminal of the resistors are connected to Vdd. As Vdd changes ur resistance values change. So connect the third terminal to OUTPUT . so that the Vdd change doesn't have the effect on the resistance values
 

good idea.

Now I simply changed the resistors to ideal ones. The output is still greatly infulenced by vdd variation.
 

i want to see the variation of OUTPUT Vs VDD plot??

1. in the schematic it looks like u shorted the bulk of PMOSes(M5 & M12) to its gate. Check the connection
 

Thanks eveybody for the your help

Problem solved!

I used a better opamp and did some other minor changes.
 

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