PSRR in bandgap reference

[circuitking]

Hi all, the below figure2 is PSRR of a bandgap reference (Vbg/Vdd).

In Figure 1

• Could you tell what do I need to do to push that floor at low frequencies to more lower values? say -90 dB
• What do I need to do to push the high frequency behavior to higher frequencies? for ex. the constant low frequency behavior should be there till 100 MHz.

Fig1 taken from Razavi's Design of Analog CMOS Integrated Circuits Second Edition

FIg2. I have taken the plot from https://picture.iczhiku.com/resource/eetop/WhkTwEqZEFFTEMBc.pdf

 

[dick_freebird]

At DC / LF it's all about the op amp AVOL (and its own PSRR, which should track but can be degraded by poor design details).

An easy improvement might be to hang the bandgap under a "poor boy LDO" (like a 4-FET stack and source follower). Bad TC will be taken out by tempco trim (presuming that's in the plan) and you ought to be able to pick up 10-20dB from flattening the internal supply before it gets to the op amp.