On Sat, 13 Mar 2004 19:38:47 +0000, Paul Burridge
wrote:

On Sat, 13 Mar 2004 10:37:13 -0800, John Larkin
wrote:

On Sat, 13 Mar 2004 16:26:10 +0000, Paul Burridge
wrote:


Okay, I've now tweaked the osc. to get as near to 50% as possible.
Alas, still no sign of any 5th present in the multiplier's output.
Here's a shot of the (fundamental) output from the inverters. I can't
see any real problem with why it shouldn't be good for a reasonable
comb of harmonics, but our experts may know better. BTW, settings were
2V/div. and 0.1uS/div.

http://www.burridge8333.fsbusiness.co.uk/trace.gif



That waveform *has* bunches of 5th harmonic. All you need is a
properly functioning bandpass filter to pluck it out.

You must have bloody good eyesight, John! :-)

You can count the graticule lines fairly well; it's close to 50%, and
the edges are fairly fast. And no, in fact I have terrible eyesight.

BTW, can you recommend a sub nS Schmitt inverter that's easily
obtainable?

I don't know of any really fast Schmitts. An HC14 followed by an AC04
should have fast edges. My favorite thing like this is an OnSemi
NL37WZ16 with all three sections in parallel. Powered from +6 or so,
it puts 5 volts into 50 ohms in something like 750 ps.

The old original RCA AC-series parts were sub-ns - crude and rude,
they were - but some ACs are now a little slower to reduce ground
bounce.

Most of the LVDS-to-TTL LVDS line receivers make damned fine
comparators with sub-ns output edges.

For screaming edges, there's always the step-recovery diode, or a
medium-power gaasfet like the CLY2.

John