Sounds like I need to do some experiments.
Thanks for the advice and idea, Bruce. :)
Ed
On 8/22/2013 12:15 AM, Bruce Griffiths wrote:
That will work to some extent however you need to tailor the stage
gain and bandwidth distribution to suit for optimum performance.
Its somewhat difficult to control the gain and bandwidth of an off the
shelf CMOS inverter and you also need to know its noise parameters.
Maybe adding resistors in series with the power supply leads of the
CMOS inveters and adding some output capacitance will suffice to
adjust the gain and bandwidth.
Bruce
Ed Palmer wrote:
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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