Two-stage OTA design - why high gain stage won't give prob?

Hi, all..

I have a simple and basic question...

Say I am designing a twe-stage ota. The first stage is for gain and the second stage is for output swing - for example, the first stage is telescopic ota and the second one is a common-source amplifier.

The small-signal gain of the first stage is 1000 and the second stage is 20.

I am wondering...if the input of the first stage is 50mV, internally the output of the first stage is then 5V???(say Vdd is 3V) - even though this two-stage ota is used in feedback system so that it has closed-loop gain of 2.

Why is this high gain stage (the first stage) not a problem???

I think I am confused with small signal and large signal concept.


Could anyone explain clearly??

The other question I have is my friend told me in 2 stage OTA with compensation, I have to crosswiring for compensation network (Cc and Rc). Do you know what that means? I think it is totally dependent on topology.


Thanks in advance
I th

Re: Two-stage OTA design - why high gain stage won't give pr

i have some metrial realted to ur OTA design,if it could help u in any means......

Re: Two-stage OTA design - why high gain stage won't give pr

check this reference.....

Re: Two-stage OTA design - why high gain stage won't give pr

check this as well.......

Re: Two-stage OTA design - why high gain stage won't give pr

this one is a IEEE reference releated to project also covering ur topic.

Re: Two-stage OTA design - why high gain stage won't give pr

Thanks...a lot.
I'll read your reference materials...Did I explain the material clearly? I am not a native english speaker..so I am just worried if my quesions were clear.

Thank you...

Re: Two-stage OTA design - why high gain stage won't give pr

hello,
i am really newbie in analog design but here is what i think >> the i/p signal is large but the feedback signal is large too , what is important is the diffrence signal "error" this is the signal which will be amplified by the OTA "high gain" , so what u need to take care of is that the o/p signal swing "u want" is working in open loop configuration (in this case u i/p very small signal = (swing u want) / (ota's gain)), as "i think" if the swing is acheivable in the open loop configuration w/o causing any transistor to go out of saturation then after u did the feedback the transistors will be OK also.
i am really not sure but this is what i could guess.
bye,
a.safwat