How to improve the gain of two stage OTA

[kkgkk]

2 stage ota

Hi, I'm new to analog circuit. I need to design a two stage OTA with gain at least 80dB. Now my circuit only has gain of 50 dB. What should I do to improve the gain? I'm using TSCM 0.4um technology. Thank you.

 

[DrBob13]

two stage, ota

Hi
This any help?
:?:

**broken link removed**

Bob.

 

[kkgkk]

Thank you, Bob.

 

[edge_tv]

First, the gain depends on the speed. faster -> lower gain (high gain needs big L, but big L means lower speed). Your topologie depends on what you want, is a two stage really needed (two stage amps need more current, but you can reach a high swing). If two, I would suggest a Telescopic input stage and a Common sourc stage as 2nd stage. Design your amp to reach your needed speed, than look for gain. Gain can be adjusted by gain boosting
Martin

 

[Sadegh.j]

try increasing the channel length of the transistors in the last stage. This usually works.

 

[jecyhale]

Hi, I'm new to analog circuit. I need to design a two stage OTA with gain at least 80dB. Now my circuit only has gain of 50 dB. What should I do to improve the gain? I'm using TSCM 0.4um technology. Thank you.

I think you can try the cascade OTA. It's gain can be as large as 800dB.

 

[ashish_chauhan]

If you are using a typical two stage miller OTA then 50dB is quite low as ur 1st stage itself can provide upto 40dB. Look into ur second stage for adding up some more gain.

If ur OTA is folded cascode one then trying gain boosting in cascodes...
for this u can refer to paper by "Bult and Geeleen" " A fast settling 90dB gain folded cascode..."

 

[mberesin]

I susgest tutorials at: **broken link removed**
It helped me a lot.

 

[RFDE]

Hi, I'm new to analog circuit. I need to design a two stage OTA with gain at least 80dB. Now my circuit only has gain of 50 dB. What should I do to improve the gain? I'm using TSCM 0.4um technology. Thank you.

I think you can try the cascade OTA. It's gain can be as large as 800dB.

i think you mean 80dB not 800dB for sure !!!

higher gain ; longer channel length , lower current , but this will affect your GBW & settling time , you need to define soecs for them

 

[analog123]

Maybe you should check your circuits,make sure all the mos satuated.

 

[yschuang]

There are many tricks experts here already recommended.
If your GBW is not so critical,you can reduce your Vgst lower to increase the gain.