I remember I saw this architecture once, but I forgot where it was.. Can anyone tell me what's this architecture for or where can I find more information on this architecture.

Thanks a lot

This actually is not an oscillator, it's an amplifier

Perhaps you are looking for a feedforward compensated opamp(?)

You may find some details about the same here
http://www.ee.iitm.ac.in/~nagendra/papers/tcas2-wlanfilter-pap.pdf

what if I add another stage of amplifier at the output of the circuit?

ULPAnalog wrote on Mar 11^th, 2016, 10:03am:

It totally depends on what you intend to do. In general adding additional gain stages to an amplifier intended to be operated in feedback requires careful considerations about stability.

can this system be stable?

Littlepotato wrote on Mar 23^rd, 2016, 11:22pm:


Why not? If there is no feedback, there will be no reason for instability.

As people have said, this looks like feedforward. Regarding stability, that is the purposes of the feedforward stage.

You have two OTAs in parallel. One uses multiple stages to provide high DC gain. Unfortunately the multiple stages will need to have limited bandwidth to achieve stability. Therefore  they put a high bandwidth single stage in parallel with it. Basically the multistage OTA acts like an open circuit at high frequency and all you have is the single stage.

I found another article from Thandri and Silva, JSSC, Feb 2003 http://amsc.tamu.edu/SIS/Publications/pub/jounal/2003_6.pdf

Feedforward is old but suffers from "doublets" which cause slow settling time. Achieving feedforward with parallel OTAs is relatively new and I don't know a lot about the drawbacks. Have any of you used this technique?