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Design >> Analog Design >> curvature on bandgap voltage reference
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Message started by coffeecat on Oct 6^th, 2005, 6:41pm

Title: curvature on bandgap voltage reference
Post by coffeecat on Oct 6^th, 2005, 6:41pm

Has anyone seen a bandgap voltage characteristic which is concave upward :) ? All of what I have seen are concave downward :( . Any comments?

Title: Re: curvature on bandgap voltage reference
Post by ericjohnson on Oct 7^th, 2005, 4:22pm

I have a design which has "concave upward" V-T characteristics. And I did see several designs in the literature as well. Check out some bandgap papers published on JSSC in the early 80's.

Title: Re: curvature on bandgap voltage reference
Post by coffeecat on Oct 7^th, 2005, 4:45pm

Thanks!

Also, how does one deal with the process variation (+/-15%) on Vbe which directly contributes to the tolerance of the bandgap voltage? The supply voltage is 1.2V.

And, how to minimize the contribution of input offset voltage (on the amplifier) to the bandgap voltage beside making the pnp's ratio larger (resistor ratio smaller) and careful layout?

Thanks!! ;D

Title: Re: curvature on bandgap voltage reference
Post by sheldon on Oct 9^th, 2005, 5:43am

Coffeecat,

You might also want to check the effect of the op-amp
input bias current. Lateral pnp transistors have low beta
and the input offset current can effect the bandgap core.

Regards,

Sheldon