Design High speed low power opamp

[sunking]

high speed op-amp

Let us dicuss how to the High speed low power opamp
First is the structure:
1 stage
2 stages
muti stages

 

[aryajur]

high speed low power opamp

You do not mention gain as the criterion, if thats the case I think 1 stage is the best option, keep the number of poles minimum. For more gain anf high speed I think 2 stage should be used and maybe Bandwidth enhancement techniques for high Bandwidths.
I am also interested in designing a very low power and high gain opamp, which can be slow, another constraint is it should be able to operate at extremely low voltages. I am trying out a 2 stage design with everything in subthreshold.

 

[sunking]

yes, I agree aryajur's suggest.
For 1 stage, if high gain is needed, we can use gain-boost tech.
For 1 stage, there is also two structure: cascode and folded cascode.

 

[ezt]

Hi.
Let's say if we want to have a low-voltage opamp, then what? I think those conventional cascode opamps or gain-boosting techs are not applicable in low-voltage circuits. However, there are some novel techniques like positive feedback amplifiers or multi-stage amps. (by saying multi-stage, I mean more than two stages. but they need complex compensation techniques.) and to make our circuit as low power as possible, I suggest using class-AB structures.

Regards,
EZT

 

[qutang]

I think two stage can get more gain,speed can be fast.

 

[sunking]

Hi, maybe for middle speed, multi stage is good.
but for high speed,multi stage(more than two) is not very power efficiency than single stage.
I have seen the UGB is about 1.9GHz single stage with gain boost amp.

 

[sunking]

for multi stage, how many kinds of compensation techniques?

 

[extraord]

what's the power efficiency of these amplifiers?
I think the current efficiency is the key factor of amp speed

 

[andy2000a]

what is your speci ??
1. High speed -> BW > 300M or 1G ?
2. low power --> current < 1m or 100ua ?

BamdWidth > 100M , I think should called video amplifier not OPA

by the way , have anyone design CMOS Current Feedback Amplifier ?? how to reduce input offset ?

 

[sunking]

hi, andy2000a,

the opa needed by pipieline adc.
not only video amplifier need high bandwith, many high speed adc need it too.

 

[sunking]

some paper about high speed opa of one stage
**broken link removed**
**broken link removed**

 

[rambus_ddr]

I also want to a high UGB opamp to design opamp RC filter. My filter bandwidth is 20MHz, so my opamp UGB is about 2GHz. I try 2 test opamp circuit.
1. two stage
since the opamp need be used with close loop, so need a 40 degree PM. when i use nulling resistor miller compensation, the miller cap is 250f, so gmI is about 1.5m, and my loading is 4p cap, so gmII is about 240m( my god, this is too large).
2. one satge with current amplifier
since current amplifier use with current mirror, which is also a pole, gm/C which is need to be larger 10G, then the current source will need very large current.
pls give your advice.

BTW sunking, can you upload the two paper about one stage high speed opa, i can't downlaod them using this link. thanks!

 

[zhaoshibin]

setting time is a most critical issue in the design of high speed opamp,espically in the application of SC circuit

 

[lyc1981]

i think 2 stage can achive high gain ,low power ,great bandwith used in pipelined adc.