Since you're looking for rise times in the low or sub nanosecond range,
why wouldn't you include any logic gates where such rise times are
inherent? I was thinking of maybe a chain of faster and faster logic
gates. For example, Potato Semiconductor - no, I'm not making that up -
PO74G04A has a risetime of < 1 ns and, if you can keep the load
capacitance low enough, a maximum input frequency of > 1 GHz.
Always trying to learn....
Ed
On 8/20/2013 11:28 PM, Bruce Griffiths wrote:
The same analysis applies however one would probably use something
like cascaded longtailed pairs with well defined gain (series emitter
feedback) and the low pass filter cap connected between the collectors
rather than opamps.
Bruce
Ed Palmer wrote:
Does anyone know if this situation would benefit from doing something
similar to a 'Collins Hard Limiter' i.e. instead of squaring the
signal in one stage, use maybe two or three cascaded stages with
increasing bandwidths? Normally, Collins limiters are used with beat
frequencies of less than 1 KHz, but maybe there's value in doing at
typical time-nuts frequencies.
Any thoughts?
Ed
On 8/20/2013 10:02 PM, Said Jackson wrote:
Hi Ed,
For anything up to about 150MHz try the NC74SZ04 types from National
if you can find them NOS. they stopped making these years ago..
Fairchild is ok too but not as fast from what I have seen.
Forgot I wrote about it in 2009. Oh boy -age kicking in.
Bye,
Said
Sent From iPhone
On Aug 20, 2013, at 20:17, Ed Palmer <[email protected]> wrote:
Hi Said,
Yes, I saw your message from 2009 where you warned about the sine
waves. That's why I was watching for it. Thanks for the warning.
I also realized that a DC Block and a 10 db attenuator makes a very
nice TTL or CMOS to Wavecrest converter for anything except 1 PPS
which would need about 15 db. I tried an old circuit that uses an
MC10116 ecl line receiver - it's actually a dead Racal Dana 1992
counter where I'm using the processing on the external reference
input to square up the signal. It gives me a slew rate equivalent
to about a 50 MHz sine wave. It helped a lot, but not enough.
I'll try a 74AC04 and a BRS2G Differential Line Receiver (risetime
< 3ns, 400Mbps throughput). Both are in my junkbox.
Ed
On 8/20/2013 8:12 PM, Said Jackson wrote:
Guys,
The dts needs to be driven by square waves, driving them with sine
waves gives jitter values that are displayed significantly too
high due to trigger noise.
Holzworth makes a small sine wave to square wave converter that
can drive 50 ohms. Use a DC block and an attenuator on the cmos
output to avoid damaging the dts inputs. You can make your own
converter using a single fast cmos gate, resistor, and blocking
cap. By using hand-selected gates I was able to achieve less
jitter with that circuit than what the Holzworth box was able to
achieve.
Doing that conversion can bring down the measured rms jitter on a
very good 10MHz sine wave source from 10ps+ to less than 2ps -
basically at or below the noise floor of the dts.. Once you run at
the units' noise floor, you know your source is quite good..
Bye,
Said
Sent From iPhone
On Aug 20, 2013, at 18:51, Ed Palmer <[email protected]> wrote:
Adrian,
I used Timelab to assess the reaction of the DTS-2077 to
different sine wave inputs. The differences in the noise floor
are surprising. The attached picture was made by taking the
output of an HP 8647A Synthesized Generator through a splitter,
and then through different lengths of cables to the inputs of the
DTS-2077. The combination of splitter and cable loss meant I
couldn't get +7 dbm @ 1 GHz. If I could have, the 1 GHz line
might have been lower than it was.
Ed
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