Bandwidth of opamp in BGR circuit

[susmitha@99]

Hi,

I designed a 2 stage opamp for my bandgap reference circuit. However, my opamp bandwidth is around 140Hz and has a gain of 104db, Unity gain frequency of 24 MHz.

Is the bandwidth enough for using it in a BGR circuit. Is bandwidth important parameter to consider while using it in BGR or my gain and UGF are enough?

Please do let me know.

Thank you in advance.

 

[dick_freebird]

The only uses for bandwidth are HF PSRR and load-step response. If
your load is constant(-ish) or heavily filtered then forget that.

You really would like to model the supply rail as a "signal" (with the
supply ripple and any random impulses from neighbor switching)
and see whether the outcome where it counts, is acceptable. Small
signal stability is only the beginning. Consequences of Vref error
is where it's at.

 

[D.A.(Tony)Stewart]

The Zout (RdsOn) is reduced by the amount of excess gain used in negative feedback. So step load response will affect the Vref error. with a switched load RC by the impedance ratio.

--- Updated Oct 12, 2023 ---

The Zout (RdsOn) is reduced by the amount of excess gain used in negative feedback. So step load response will affect the Vref error. with a switched load RC by the impedance ratio. If using a complementary common source output then you have a tradeoff between Zout and quiesent current.

 

[susmitha@99]

The only uses for bandwidth are HF PSRR and load-step response. If
your load is constant(-ish) or heavily filtered then forget that.

You really would like to model the supply rail as a "signal" (with the
supply ripple and any random impulses from neighbor switching)
and see whether the outcome where it counts, is acceptable. Small
signal stability is only the beginning. Consequences of Vref error
is where it's at.

okay, so I should concentrate more on my Gain-Bandwidth product, rather than open loop bandwidth?