LMH6722: Fanout analog signal

DeWei Lan

Part Number: LMH6722
Other Parts Discussed in Thread: OPA3693

Our signal is about 2 ns falling time(500mV->300mV) of negative pulse.

like here:

I'd like to fanout a signal from 1 to 8.

I think using LMH6722*2 to make fanout circuit, which signal I/O is from the func-gen through fanout board, finally go to scope.

If I just adopt LMH6722*2, in addtion to "50-ohm I/O terminated impedance matched", what should I care about?

LDO is necessary?

My basic consideration as following picture.

Where are can be improved?

Could anyone give me suggestion?

over 3 years ago

+1 kai klaas69 over 3 years ago

Guru 140200 points

Hi Dewei,

this would be the result:

dewei_lmh6722.TSC

Better to do it this way, as recommended in the datasheet:

Or like this, to overcome the cable dampening:

Kai

0 Alec Saebeler over 3 years ago in reply to kai klaas69

TI__Mastermind 22704 points

Hello DeWei,

Could you update us if/when you try one of Kai's methods, or have any follow-up questions?

Best,

Alec

0 Michael Steffes over 3 years ago in reply to kai klaas69

Guru 48395 points

Another solution to consider is some of the triple fixed gain video buffers, a part like the OPA3693 is shown driving 75ohm cables, but can work as well with 50ohm - could use 3 of those and disable 1 channel. at a gain of 2 as Kai shows, this one is a little faster than the LMH6722. All of these are current feedback so you need to operate with some feedback R for stability. And, the layout for these triple (intended as RGB drivers) is much better than the quad op amp pinout,

https://www.ti.com/lit/ds/symlink/opa3693.pdf

Amplifiers

Amplifiers forum

LMH6722: Fanout analog signal