Re: The emitter-coupled monostable as slow differential amplifer

On 21/07/2024 7:04 am, john larkin wrote:

On Sat, 20 Jul 2024 15:29:58 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
 

About a month ago John Larkin dismissed the emitter coupled monostable
with "It's really a slow diffamp, not a one-shot."
>
If you feed a really slow pulse into it, it can look that way.
The 3.3pf capacitor at C1 doesn't feed through much current if you drive
the input with a slow edge
>
The simulation below demonstrates it working exactly that way.
>
No sensible circuit designer would deliberately drive it with a very
slowly rising and falling pulse  - if you want it to work as a
monostable pulse stretcher, you have to drive it with a pulse that is
narrower than the one you want to get out.
>
Integrated circuit monostables don't have that limitation, but they are
more complicated, and slower. There was an ECL monostable that went down
to 10nsec, but the emitter-coupled monostable lets you get down to
1nsec, if you use it right.
>

 That wasn't my point. My comment wasn't about the trigger risetime but
that if you put in a long trigger, you get a long output. It's hardly
a one-shot.  The input and output levels are weird too.

The emitter-coupled monostable has been around for ages, and it's limitations have been well-known for just as long.

If course a proper one-shot should fire cleanly on a fast or slow
rising edge.

Sadly, proper one-shots can't produce a 1nsec wide pulse. If you need that, you have to settle for a less-than-proper one-shot.
Skilled circuit designers know about those kinds of compromises, and find work-arounds.
<snipped the elaborate - if totally unjustified - circuit diagram.>
John Larkin seems to confuse discussion and willy-waving.
--
Bill Sloman, Sydney
--
This email has been checked for viruses by Norton antivirus software.
www.norton.com