DC to >100MHz Wideband Amp

I don't exactly know what you mean by "digitally drive a PIC..." Maybe the LM6702 would suit your needs?

--Mac

What gain?

What input impedance?

What DC offset voltage is acceptable?

How close does the signal need to get to the rails?

What do you mean by "digitally drive"?

What supply voltage?

The jellybeam solution for small signals is a MMIC. It'll have way more bandwidth than you need. But they're pretty much unconditionally stable by themselves.

You said DC, but didn't say anything about gain, voltage ranges, etc., so I feel justified in recommending the MMIC :-). Biasing the input will be your problem.

I have no clue what this phrase means. Are you building a frequency counter maybe? There are a lot of examples of input-conditioning circuits for frequency counters on the web. Some of them even work!

Tim.

Thanks for your message. I'm finally getting back to this. Sorry I wasn't clearer before.

The input will be about 100Mv Hi impeadance, say 100K and the out put is to drive a TTL input to a counter. So the offset is negligble as long as the output swings from roughly ground to 3.5v, TTL levels. The available supply is 5 to 6VdDC 100Ma.

Thank you very much.

Sincerely,

Dave

Thanks for your message, Mac. I'm finally getting back to this. Sorry I wasn't clearer before.

The input will be about 100Mv Hi impeadance, say 100K and the out put is to drive a TTL input to a counter. So the offset is negligble as long as the output swings from roughly ground to 3.5v, TTL levels. The available supply is 5 to 6VdDC 100Ma.

I'll look into the LM6702

Thank you very much.

Sincerely,

Dave

Thanks for your message, Tim. I'm finally getting back to this. Sorry I wasn't clearer before.

The input will be about 100Mv Hi impeadance, say 100K and the out put is to drive a TTL input to a counter. So the offset is negligble as long as the output swings from roughly ground to 3.5v, TTL levels. The available supply is 5 to 6VdDC 100Ma.

I gave the MMIC a look, but need to spend more time researching it. Plus search for counter input circuits as you mentioned.

Thank you very much.

Sincerely,

Dave

You might want to investigate the Linear Technology IC LT1016 which we use as a squaring circuit for a low level sine wave

I am not certain as to it's upper frequency limit, but in general it would serve as a sine to TTL converter nicely.

Of course, you might want to make a FET follower to keep the RF input high impedance.

Jim Pennell

He said 100 MHz from 100k. With the LT1016's 3.5 pF input capacitance that gives a -3dB frequency of 455 kHz. But I doubt that he means that.

Jonathan

would a cmos inverter do ? maybe a simple level shifter to get the input to about half the supply voltage.

Colin =^.^=

OUCH. Yep, 3.5 pF would be a problem. We are using it at 10 MHz, and for our purposes, the sensitivity is quite good. Although, we do use an input filter network and I will analyze it to see if we are absorbing the 3.5 pF into the filter.

Jim

"Jonathan Westhues" a écrit dans le message de news:Jlvoe.24996$ snipped-for-privacy@news20.bellglobal.com...

Unless some _very_ special case, it can't be 100k @ 100MHz : this is only

He'd better refine his specifications.

Or maybe he is unfamiliar with the concept of a comparator and is using the 5th harmonic rule for reproduction of a 20MHz pulse train- but even then 100K seems high- and notice that DC makes no sense at all since he mentions nothing about level or gain into the PIC- just anything that crosses logic thresholds.