resetting a filter

Saturation is about nonequilibrium charge density in the base region, which shields out the E field in the junction. It's the collector current that scavenges all the injected carriers from the base, so I would think that your situation would have all the nasty charge storage problems of recovery from saturation.

Cheers

Phil Hobbs

How about a little piece of coax? Or wind the pcb trace around the board?

or lumped element delay?

George H.

So I figure

.highlandtechnology.com=A0 jlarkin at highlandtechnology dot com

Somewhere there is a famous video of a presentation by a older female military officer (Navy?) where she holds her fingers about

Ahh, I found a link, not the one I remember, but good.

Her name Grace Hopper.

Mikek

Grin, yeah I was looking at an Ortec delay generator 425A the other day.

George H.

what is a "few"? 3, 6, 22? How accurate of a delay?

If it's less than 15 or so take a 74lvc04 running at 3.3 will give you a tpd typical of 2.5ns per gate. Wire 2,4 or 6 to get 5, 10 or 15ns.

It's hard to pick-and-place two feet of coax!

Or wind the pcb trace around the

That would take a couple feet of trace, and it's not tunable. The board will be pretty small.

This *is* lumped element delay!

Oh well, I guess I'll use diodes.

She is also the one who introduced "bug" into our language for a problem in the equipment.

It would be good if I could change parts values to tweak the delay to sub-ns resolution. I can do that with an RLC circuit.

What does "recover quickly" mean? After a positive-going transition how soon does a negative-going transition occur? ...Jim Thompson

ge

vary the supply voltage?

or maybe a single gate with a resistor in the supply? might make pull up slower than pull down

-Lasse

Now, I'm really confused. If coax would meet the electrical requirement, why do you need to reset your filter??? Sounds like you want to shorten the pulse by delaying the front edge.

More info about the range of pulse rates and widths might be relevant.

IIRC her notebook says something like "First actual bug found in logic system", because there was a moth or something stuck in there. That remark seems to show that the phrase "getting the bugs out" was already in use.

Cheers

Phil Hobbs

Farnell in Europe is still selling Filotex 1.22mm OD 75R coax. You could wind a metre or so of that onto a RM core former and place it like any other component.

Newark doesn't seem to stock it, so you'll have to go a different distributor

Not if you are planning to use active parts to "reset" it (which seems like a very bad idea).

-- Bill Sloman, Nijmegen

That would more than fill up the entire volume of the instrument I have in mind.

Why is it a bad idea? It will certainly work, namely give me a delay that resets quickly.

Ancient problem, ancient solution. Just use a stupid RCD delay. (R || D) + C, use a schottky if your V_IL is tight.

Tim

-- Deep Friar: a very philosophical monk. Website:

My thoughts exactly.

Proper selection of the DIODE and R type (not value) is key though.

Jamie

Yes, Adm Grace used to hand out "nanoseconds" (a foot long piece of wire) when she gave presentations. A former boss had one of hers.

How do you figure there's no c-b current. The path from /Q thru b-c and back to Q looks like a forward biased c-b current path?

On Tue, 7 Aug 2012 19:38:01 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Q looks like a forward biased c-b current path?

Yeah, there will be current in that direction, the opposite direction from "normal" collector current. I guess that will load carriers into the c-b junction and add turn-off delay.

A schottky diode discharges the filter pretty well, but I'd like to kill it all the way ASAP, so it forgets a pulse as fast as possible before the next one hits.

Version 4 SHEET 1 880 680 WIRE 112 -240 -16 -240 WIRE 240 -240 192 -240 WIRE 368 -240 320 -240 WIRE 464 -240 368 -240 WIRE 528 -240 464 -240 WIRE 368 -208 368 -240 WIRE 368 -112 368 -144 WIRE -16 -32 -16 -240 WIRE 16 -32 -16 -32 WIRE 80 -32 16 -32 WIRE 368 -32 144 -32 WIRE -16 144 -16 -32 WIRE 96 144 -16 144 WIRE 224 144 176 144 WIRE 368 144 368 -32 WIRE 368 144 304 144 WIRE 464 144 368 144 WIRE 512 144 464 144 WIRE -16 160 -16 144 WIRE 368 176 368 144 WIRE -16 272 -16 240 WIRE 368 272 368 240 FLAG -16 272 0 FLAG 368 272 0 FLAG 368 -112 0 FLAG 464 144 OUT FLAG 464 -240 REF FLAG 16 -32 IN SYMBOL res 320 128 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 200 SYMBOL cap 352 176 R0 SYMATTR InstName C1 SYMATTR Value 10p SYMBOL ind 80 160 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L1 SYMATTR Value 330n SYMBOL voltage -16 144 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 WINDOW 3 -441 -22 Left 2 SYMATTR InstName V1 SYMATTR Value PULSE(0 3.3 1n 400p 400p 5n 10n 2) SYMBOL diode 144 -48 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName D2 SYMATTR Value DID SYMBOL ind 96 -224 R270 WINDOW 0 32 56 VTop 2 WINDOW 3 5 56 VBottom 2 SYMATTR InstName L2 SYMATTR Value 330n SYMBOL res 336 -256 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R2 SYMATTR Value 200 SYMBOL cap 352 -208 R0 SYMATTR InstName C2 SYMATTR Value 10p TEXT 80 72 Left 2 !.tran 30n TEXT -616 0 Left 2 !.model DID D(Vfwd=0.3 Ron=12 Roff=1G Cjo=0.2p)