Attenuator circuit

[Boncuk]

Bon, did you have a look at the part I posted? It looks like it might make a good front end for a counter. Appears to work at 100MHz at 10mv input.

Yes Mike,

I did right away. The frequency range is higher I need.

All I want is to clip input signals higher than 5V and amplify the weak inputs (<3V).

That way the counter could be used to measure CMOS circuits with an output of 12V.

I made a prescaler circuit 1:1000 (for decade counting) and variable gate times stepping up in decades from 10µs to 10s. (10s for freaks wanting to measure mains frequency and fractions thereof.)

The only thing I'm worried about is frying the input circuit by applying voltages >VCC.

Kind regards

Hans

 

[Nigel Goodwin]

Yes Mike,

I did right away. The frequency range is higher I need.

Like I've said all along, that's an unrealistic requirement - high speed prescalers requires matched 50/75 ohm connections.

All I want is to clip input signals higher than 5V and amplify the weak inputs (<3V).

That way the counter could be used to measure CMOS circuits with an output of 12V.

I made a prescaler circuit 1:1000 (for decade counting) and variable gate times stepping up in decades from 10µs to 10s. (10s for freaks wanting to measure mains frequency and fractions thereof.)

Gives you greater resolution, which is the normal reason for very slow ranges, but they are really boring to use I think mine at work has a 100 second range?.

The only thing I'm worried about is frying the input circuit by applying voltages >VCC.

I've already given you a suitable cirucit for 50Mhz and below - once you start using prescalers they don't really apply, not even on commercial counters.

 

[Boncuk]

I've already given you a suitable cirucit for 50Mhz and below - once you start using prescalers they don't really apply, not even on commercial counters.

Are commercial counters limited to 5V input only?

The prescaler I use has an input impedance of 50Ω. (to be precise 51Ω)

 

[Nigel Goodwin]

Are commercial counters limited to 5V input only?

No, but it's a pretty limited range, and not very sensitive (compared to the lower frequency ranges). As it's 50 ohm you can easily reduce any high voltage inputs with simple pie attenuators - you can even buy them ready made.

 

[atferrari]

I could help

Never worked with ECL but I could eventually help you here...

1,000.000.000 US$ on my bank account. (unable to spend till the end of my life).