what can i do to enhance the bandwidth of an OP?

[daisyinfall]

the current was limited in 200uA,and the load capacitor was 12p,the dc gain should be 80db,how can i get a bandwidth of 40M? (0.5u technics)
anyone help me?

 

[wossy]

Re: what can i do to enhance the bandwideth of an OP?

You do not provide enough information, such as the device you are using. Have you tried consulting the datasheet?

J

 

[sunking]

what can i do to enhance the bandwideth of an OP?

big W/L can help you.

 

[huojinsi]

Hi sunking

big W/L can help you.

Why? Pls describe the detail. Thks!

 

[beckchm]

Using special configuration.

 

[Humungus]

You are talking gain-bandwidth product of 20MHz. For a single stage amplifier, with a load of 12pF, this means a gm of 1.5mS (2.pi.fT=gm/CL). Assuming a gm/Id of at least 10, this gives us an Id of the input transistors of 150uA per transistor, which makes a total current of at least 300uA. So you need a class AB output stage to get and fT of 20MHz with that load and current consumption. Anyway, I guess it would be very difficult to reach such a goal.

Maybe with a gm/Id of 15 and a two- (or three-) stage configuration it can be possible. Is it on CMOS or bipolar?

 

[daisyinfall]

Thanks so much.
Hi,Humungus.It is on cmos.

The requirement of dc gain is 80db,so I think two stage is necessary.For low 1/f noise,pmos input pair is applied.I have tried (w/L)9 to 600/0.6,but it is of no use.
The terminal value GBW of this OPamp is aboat 24M.what can i do to elevate the GBW to 40M.
I have been suffering from this for two weeks ....

Thank you for any suggestion![/img]