mohamis288
Full Member level 3
Hello,
the following image, shows a two-stage class AB operational amplifier ( from "THE DESIGN OF LOW-VOLTAGE, LOW-POWER SIGMA-DELTA MODULATORS" );
this amplifier has two common-mode feedback circuit, and so, here is the proposed schematic:
the second stage CMFB is placed in the attachment, and I know how it works. but I do not know the second stage CMFB. Voutp and Voutn are the output voltage. Vmid is the desired CMFB, but what about Vcs2, Vcs3. how can we determine them? in the image below. you see the first stage CMFB. in this circuit, Vcmfb1, is connected to the tail current source. so, we know how feedback returns to our circuit. But, in the second stage CMFB, HOW does the feedback return to our circuit?
Oh sorry, after the image of "CMFB of the second stage", I've wrongly written that "the second stage CMFB is placed in the attachment, and I know how it works.". I meant I know how CMFB of the first stage
Works. But I have problem with the second stage CMFB.
the following image, shows a two-stage class AB operational amplifier ( from "THE DESIGN OF LOW-VOLTAGE, LOW-POWER SIGMA-DELTA MODULATORS" );
this amplifier has two common-mode feedback circuit, and so, here is the proposed schematic:
the second stage CMFB is placed in the attachment, and I know how it works. but I do not know the second stage CMFB. Voutp and Voutn are the output voltage. Vmid is the desired CMFB, but what about Vcs2, Vcs3. how can we determine them? in the image below. you see the first stage CMFB. in this circuit, Vcmfb1, is connected to the tail current source. so, we know how feedback returns to our circuit. But, in the second stage CMFB, HOW does the feedback return to our circuit?
--- Updated ---
Oh sorry, after the image of "CMFB of the second stage", I've wrongly written that "the second stage CMFB is placed in the attachment, and I know how it works.". I meant I know how CMFB of the first stage
Works. But I have problem with the second stage CMFB.
Last edited: