Low Voltage Rail to Rail op,who could give me some advice ?

[lghhust]

I am designing a low voltage(below 1 Volt) rail to rail op,and the veriation of that op needs to be kept in 5% in the whole supply range ,could anyone geive me some advice?
thanks a lot.

 

[naalald]

Re: Low Voltage Rail to Rail op,who could give me some advic

Hi,
This paper by chatterjee will help you.

 

[lghhust]

bulk driven may cause lager gm variation,though get lager input range.I will find if there is any way to compenstate this variation.
thanks a lot!

 

[abcyin]

Hi,
You can use the constant gm bias circuit to compensate the variation.

hope it helps!

 

[jeepx5]

a book named low voltage opamp will be helpful

 

[yschuang]

Re: Low Voltage Rail to Rail op,who could give me some advic

As I know, constant gm biasing ciucuits is used for rail to rail input swing to reduce the variation on the gm of input stage, which makes unity gain frequency more stable. By the way, what do rail to rail mean ? Rail to rail in the input or output stage. If you need a rail to rail input, pmos and nmos input pairs are needed. Try to find a professor named Huijsing and he has many publications on opamp.

 

[s_babayan]

Re: Low Voltage Rail to Rail op,who could give me some advic

Dear Friend

You can use three or two low-voltage analog design technique to achieve good responce, for inputs I recommend you to use Bulk-driven PMOS inputs, then you can use level-shifter approach or subthreshold biasing to improve you power and Low-voltage responce .

Hope it helps you my friend.

Good luck

 

[gte582w]

as for the input, it seems that you have to use bulk driven as o/w, VDD need to be at least 2 VTH to cover rr, which is > 1V already. It's gonna be a tough problem for sure.

 

[lghhust]

thanks a lot!
the |Vth| in my circuit is about 0.4. I biased imput diff pairs in weak inversion and it appaered that a zore is in RHP at about 1M, I felt frustrated and don't know what's the reason.
To yschuang
It might increase mismatch by using pmos and nmos input pairs togather,so I use current switch.
To s_babayan
I found that with level-shifter,ac simulation appeared a higher gain and poor PM,I could not find what's the reason.

 

[rosaeidi]

Hi

see