What are these two circuits?

[alankim]

What are this circuit? It looks like some sort of current mirrors but I am trying to understand what it is and what the merits/drawback of it. Has anyone seen this before? Appreciate that you share your experience!

[Dominik Przyborowski]

These two circuits are an ultra high swing current sources (on the first schematic is lack of biasing branch for VBN and VCN so it hard to call it as mirror).
The first one was presented first time (as my best knowledge is) at 2002 in the IET Electronics Letters (don't remember details), while second was published in Elsevier Microelectronics Journal ca 2011.

The first one using only negative feedback (there is double boosting applied) to achieve the most flat output characteristic with output resistance in range of K_1×K_2×K_4×r_3 (where K is an intrinsic gain of each mosfet) and can have very low Vout_min (my experience is as low as 25mV, however it is set by biasing circuit). Due to high gain feedback it would required compensation at gate of M1.

The second circuit has using both negative and positive feedback loop (M3→M1→M2→M4 which are moving minimum Vout to lower values), and now I have seen this circuit is not a mentioned by me UHS CM from MJ_2011 . It doesn't has a 3 MOSFETs for negative feedback boosting an output resistance. If you could share with more info where did you found the second scheme, it would be useful to discuss.

[CAMALEAO]

How does the second has.negstive feedback? Can't see it/follow. Can you explain please.

[Dominik Przyborowski]

I didn't look closely to the second scheme and I was misled by my mind, what I have noticed during writing the post

The circuit which I had on mind is published here:
https://www.sciencedirect.com/scienc...26269210002326
And it contains a three more mosfets (current source output transistor and CS amplifier) composing mentioned by me negative feedback.

The scheme on post #1 has not negative feedback obviously. My mistake.