[time-nuts] More on paralleling output gates

[John Ackermann N8UR]

This morning I took 'scope shots of three 74AC04 gates paralleled
through 47 ohm resistors, and of a single gate through a 47 ohm resistor.

There's very little difference in rise time -- 2.5ns (10% to 90%, using
the post-ringing high level as 100%) for three gates, and 2.35ns for a
single gate.  As expected, the output voltage using a single gate was
significantly lower; the three-gate voltage was  3.56v p-p while the
single-gate voltage was 2.32v p-p.

The test setup was an HP 5363 time synthesizer set to generate a 1MHz,
50% duty cycle square wave through a 4 foot RG-58 cable driving a TADD-3
board set for 50 ohm input termination.  The TADD-3 output went through
a 4 foot HP 50 ohm test cable (the ~RG-58 thickness, highly flexible,
gray jacket type) into a Tek 2465B 400MHz scope with 50 ohm internal
termination.

John
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