why the slope is different in my bandgap simulation

EDAboard.com Forum Index -> Analog IC Design & Layout -> why the slope is different in my bandgap simulation

Author

Message

wangkes9

Joined: 10 Jan 2008
Posts: 43

29 Jun 2009 4:21 why the slope is different in my bandgap simulation

In my simple bandgap design , I simulation the slope of Vbe and delta Vbe in TSMC
technology. But the slope of delta Vbe is not k/q(lnn), much smaller. so I have to increase the ratio of R1/R0. So the Vref is not 1.25V , almost 2V

What is wrong? I sim the circuit in chartered technology ,It is the same.

Google
AdSense
Google Adsense

29 Jun 2009 4:21 Ads

Sorry, but you need login in to view this attachment

saro_k_82

Joined: 17 May 2007
Posts: 266
Helped: 55
Location: India

29 Jun 2009 4:48 Re: why the slope is different in my bandgap simulation

This is most probably because all your bulks are open and are at different potentials. There is an offset of more than 25mV on VBE voltage, which can cause high current asymmetry as well.