[time-nuts] More on paralleling output gates

Chuck Harris cfharris at erols.com
Sun Apr 9 23:34:29 EDT 2006

Magnus Danielson wrote:
> From: "Robert Lutwak" <Lutwak at Alum.mit.edu>
> Subject: Re: [time-nuts] More on paralleling output gates
> Date: Sun, 9 Apr 2006 16:04:49 -0400
> Message-ID: <001401c65c10$db4f3070$6400a8c0 at lutwakhome>
>> I suspect you're just measuring the bandwidth of your 400 MHz oscilloscope.
> He is close... tau of 1.1 ns should be expected from a 400 MHz.
> I am sitting here and thinking "Hey, isn't those 3 x 50 Ohm sources in parallel
> a impedance missmatch?". If you have a sufficiently long system (> 1/12 of the
> risetime in cable-length which in this case would mean maybe 50 cm or so) we
> must consider it as an impedance system and thus we should care less about the
> bulk capacitance behaviour (which can be "cured" with a stronger source) but
> rather with the source and load impedances relative the cable impedance.
> I'd like to view the exercise as only mildly interesting. Better to find a
> better source for that signal. If you feel like toying around more on that '04
> then directly parallel the outputs into a single 47 Ohm resistor might be more
> productive.

Which would be exactly the same as putting 150 ohm resistors in series with
each of the three outputs, and tying them all together in parallel.

Which will produce a pulse that is 1/2 height when terminated with 50 ohms...
hardly TTL.

-Chuck Harris

More information about the time-nuts mailing list