Simple pulse stretcher

about it.

Naturally.

Are you planning on designing stuff that surface

No, onto mine. My output would be a coax connector.

You say that like it's a bad thing.

Tek service manuals used to be quite explicit about setting up Y amplifiers for minimum overshoot and ringing. Properly set up, the correlation between 3dB bandwith and rise time, using the 0.35 rule of thumb was quite close. Nearly every vertical amplifier I've come across, apart from the 50 ohm ones, has been overcompensated at the HF end.

Lowpass. DC to whatever.

ln(9)/(2*pi), 0.3496

At that

ing about it.

Do you have a specific connector in mind? SMA crapped out at 18GHz. Somebody has obviously introduced something better since then, but Farnell wasn't stocking whatever it is when I last looked,

It's true that there is a deliberate ambiguity there.

He's certainly the most copious poster here over the long term - 31024 posts. Eeyore is still second at about 19,000, I'm third with 18393 and Jim is fifth at 17611, just after Mike Terrell.

The Google statistics don't separate on-topic and off-topic posts. My impreesion is that Jim Thompson posts a higher proportion of off-topic stuff than John Larkin, but it isn't the kind of question for which it's worth going to the trouble of finding an answer.

that

about it.

ps

that

about it.

ps

Whatever the load (a lithium niobate EOM) uses, I guess. 2.5 mm maybe, which is SMA matable. I'd want PCB edge-launch. Launching into the connector is the scary part.

If you get obnoxious again, I'll ignore you again. Your call.

Here it is:

Frankly, Tektronix is cheating.

that

about it.

Indeed! Technical discussion without insult. I'll remove Sloman's filter ;-)

As for Larkin... he only shows boxes, never a WORKING schematic, or one that can be verified.

Now-a-days, 500MHz CMOS is passé. ...Jim Thompson

rote:

th layout using that parts family. It used to be a point of advantage for a logic family that it was unresponsive to full logic level transitions of d uration less than the fastest edge rates in the system. Interwiring capacit ive coupling into a nice high impedance input converts the transition into a nice square pulse there. I think Lenin covered that one.

One-shots are really chunks of analog electronics, and don't fit perfectly into all-digital systems. Decoupling the 5V supply at the monostable to the wrong 0V track can be a real problem.

If the track running from the monostable to the timing capacitance is too long, or runs close up against an active trace, cross-talk can make the output pulse lengths erratic. Analog designers tend to be conscious of stuff like that. Digital designers tend to over-simplify and find out the hard way.

layout using that parts family. It used to be a point of advantage for a logic family that it was unresponsive to full logic level transitions of duration less than the fastest edge rates in the system. Interwiring capacitive coupling into a nice high impedance input converts the transition into a nice square pulse there. I think Lenin covered that one.

One-shots are politically incorrect, the legacy of days past when far too many people designed asynchronous, hazardous, glitchy hairballs. Moto sold a DTL part that was absurdly noise sensitive, and that contributed to the bad reputation.

They can be handy, used carefully.

There is? It seems that is a result only for normal distributions.

with layout using that parts family. It used to be a point of advantage for a logic family that it was unresponsive to full logic level transitions of duration less than the fastest edge rates in the system. Interwiring capac itive coupling into a nice high impedance input converts the transition int o a nice square pulse there. I think Lenin covered that one.

Yup, I'll do the schematic and look over the layout. I was drawing on the white board and explaining the circuit to 'the boss' and I drew a line between the comparator and first HC14, this sides analog, that's digital, The diode RC thing is on the analog side of the circuit, I'll put the one shot in the same place.

George H.

ith layout using that parts family. It used to be a point of advantage for a logic family that it was unresponsive to full logic level transitions of duration less than the fastest edge rates in the system. Interwiring capaci tive coupling into a nice high impedance input converts the transition into a nice square pulse there. I think Lenin covered that one.

many

TL part

tion.

.highlandtechnology.com  jlarkin at highlandtechnology dot com

The last time I used a one shot was back in '93. (real TTL) Two of them set the pulse lengths in a NMR spectrometer.

George H.

layout using that parts family. It used to be a point of advantage for a logic family that it was unresponsive to full logic level transitions of duration less than the fastest edge rates in the system. Interwiring capacitive coupling into a nice high impedance input converts the transition into a nice square pulse there. I think Lenin covered that one.

many

part

reputation.

Incwww.highlandtechnology.com  jlarkin at highlandtechnology dot com

I rarely use "one-shots", but I regularly use "stretchers" in my custom chips... follows input up, then delayed drop-out. ...Jim Thompson

Yup. From the derivative theorem, the variance is proportional to the second derivative of the transform, evaluated at zero frequency. To within a constant factor that depends on your Fourier transform definition,

int(-inf to inf) [t**2 * h(t)] var(h) = ------------------------------- = H''(0)/H(0) int(-inf to inf) [h(t)]

Because the function is real, its transform is Hermitian, i.e. the real part is even and the imaginary part is odd. Even-order derivatives of an odd function vanish at the origin, as do odd-order derivatives of an even function.

When you convolve g(t) and h(t), the transform is G(f)H(f). The variance of this is proportional to the normalized second derivative at the origin, as before. Ignoring a possible constant of proportionality that we don't care about,

d(GH)/df = GH' + HG' so

d**2/df**2[GH]| H(0)G''(0) + G(0)H''(0) + 2G'H' var(g*h) = --------------| = ------------------------------- GH |f=0 H(0)G(0)

G''(0) H''(0) 2G'(0)H'(0) = ------- + -------- + ------------ G(0) H(0) H(0)G(0)

The first term is the variance of G, the second is the variance of H, and the third is zero if either G or H is an even function.

There is a slightly more subtle condition that will make the third term zero for any choice of g and h: that the first moment of either h(t) or g(t) is zero, i.e. that at least one of them has its centroid at t=0, which makes its first derivative zero at f=0.

It is always possible to satisfy this condition by an appropriate choice of the time origin, so if you'll allow me to slide over that rather trivial issue(*), variances add under convolution.

Cheers

Phil Hobbs

(*) The reason for this is the effect of a shift of origin on the variance. If you convolve a function centred at t=5 with one centred at t=3, the convolution's centroid is at t=8. If you're computing the variance as the second moment about t=0, this will make a big difference, but it doesn't change the shape of the resulting convolution function. Forcing one of them to have its centroid at 0 gets rid of this shift of time origin.

n,

H''(0) + 2G'H'

-----

at

Awesome... (Be careful what you ask for.)

Phil, If I mix two lasers together on a photodiode and look at the bandwidth of the beat note to measure the laser bandwidth.. Is the measured bandwidth the quadrature sum of the individual lasers (as above for rise times, noise..) or does the power law nature of the PD put a twist on it?

George H.

layout using that parts family. It used to be a point of advantage for a logic family that it was unresponsive to full logic level transitions of duration less than the fastest edge rates in the system. Interwiring capacitive coupling into a nice high impedance input converts the transition into a nice square pulse there. I think Lenin covered that one.

many

part

reputation.

Incwww.highlandtechnology.com  jlarkin at highlandtechnology dot com

They are handy for winking LEDs. And there is my almost-famous double-tach/FM discriminator circuit: