signal indicator

John Larkin wrote in news: snipped-for-privacy@4ax.com:

That should drive it fine. At 2V I am sure you won't have any false threshold read issues.

I suppose I could clock a 1 into an ECL flipflop, and clear the flop at, say, 1 KHz. The flop would drive the LED. That's a more 'official' design, a bit more expensive maybe.

What I've done (not knowing the duty cycle of a signal pulse) is toggle a flipflop. On anything regular, that makes a 50% duty cycle square wave.

Flipflops have true/invert outputs, so a capacitor-resistor limiter into a back-to-back LED pair makes indicator that only lights up when there's logic transitions.

This one was battery-powered, sensing a TTL pulse.

maybe use transistors instead of diodes?

You could measure the current taken by the buffer. Well, you did say 'any other ideas'.

Cheers

Just two NPNs might be enough:

piglet

Looks OK to me--you might not need detectors in both leads.

Cheers

Phil Hobbs

just add Rs in series with your 10pF pickoffs.

Oh, you can also simplify it if you don't mind it missing a single transition one way only. Signal thru C, R to ground, through R into tr. Add collector led/r. Job done.

NT

I think you should go with the detector chip.

They are not cheap. May as well use a flipflop, which we have in stock.

That would be zero risk and would work to arbitrarily low frequencies. The ECL loading is entirely orthodox.

Adding a new part to the PADS library, and to stock, is a chore.

With 2 volts p-p on two lines, a diode detector should be safe too.

A BFT25 rectifying emitter follower would be interesting.

At 2 GHz, I'd need an ECL flipflop, and that only swings 0.8 volts.

With an ECL flop, this would work:

Yes. BFT25 maybe, 5 GHz Ft.

ECL supply current is pretty much constant with frequency.

I thought the symmetry was pleasing, with equal loading on each logic line. I guess I have lots of signal, by RF standards, so one zero-bias detector should work fine.

Even one diode should work.

I'm OK with your flip flop idea, standard fast parts. I was worried about up to 2GHz with ordinary diodes.

, which we have in

We stock an SMS7621, which is a tiny 0.25 pF schottky. 16 cents each.

It's a low barrier part, and I have 2 volt swings so it should be OK as a zero-bias detector or doubler.

This is RF, and I don't do RF!

Hey, maybe I could make a directional coupler or two out of PCB traces instead of the capacitor pickoffs.

On 3 May 2019 09:55:36 -0700, Winfield Hill wrote:

This works surprisingly well, good output from 500 KHz to 2 GHz. C1 would be bigger in real life. There's just a 5 pF load on the ECL.

Version 4 SHEET 1 880 680 WIRE -304 96 -576 96 WIRE -80 128 -160 128 WIRE -16 128 -80 128 WIRE 96 128 48 128 WIRE 128 128 96 128 WIRE 208 128 128 128 WIRE 336 128 272 128 WIRE 480 128 336 128 WIRE 512 128 480 128 WIRE -304 160 -464 160 WIRE 336 160 336 128 WIRE 512 160 512 128 WIRE -576 176 -576 96 WIRE 128 176 128 128 WIRE -464 208 -464 160 WIRE 128 288 128 240 WIRE 336 288 336 240 WIRE 512 288 512 224 WIRE -576 320 -576 256 WIRE -464 320 -464 288 FLAG 128 288 0 FLAG 336 288 0 FLAG 512 288 0 FLAG -80 128 GEN FLAG 480 128 OUT FLAG 96 128 MID FLAG -576 320 0 FLAG -464 320 0 SYMBOL diode 144 240 R180 WINDOW 0 -45 25 Left 2 WINDOW 3 -41 -4 Left 2 SYMATTR InstName D1 SYMATTR Value Ds SYMBOL diode 208 144 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D2 SYMATTR Value Ds SYMBOL res 320 144 R0 WINDOW 0 67 46 Left 2 WINDOW 3 49 78 Left 2 SYMATTR InstName R1 SYMATTR Value 100K SYMBOL cap 496 160 R0 WINDOW 0 61 20 Left 2 WINDOW 3 53 57 Left 2 SYMATTR InstName C1 SYMATTR Value 50p SYMBOL cap 48 112 R90 WINDOW 0 80 36 VBottom 2 WINDOW 3 87 32 VTop 2 SYMATTR InstName C2 SYMATTR Value 5p SYMBOL SpecialFunctions\\modulate -304 96 R0 WINDOW 0 45 -55 Left 2 WINDOW 3 -46 -93 Left 2 SYMATTR InstName A1 SYMATTR Value mark=10Meg space=0 SYMBOL voltage -576 160 R0 WINDOW 0 -107 91 Left 2 WINDOW 3 -291 129 Left 2 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value PULSE(0 1 0 200u 0 1) SYMBOL voltage -464 192 R0 WINDOW 0 71 38 Left 2 WINDOW 3 57 71 Left 2 SYMATTR InstName V1 SYMATTR Value 0.75 TEXT -336 352 Left 2 !.MODEL Ds D(IS=130n RS=4.5 N=1.08 XTI=1.8 EG=.68\n+ CJO=260f M=.047 VJ=.11 FC=.5 BV=4 IBV=10U TT=25p) TEXT -208 280 Left 2 !.tran 100u TEXT -16 -16 Left 2 ;SMS7621 Diode Detector TEXT 48 24 Left 2 ;JL May 3 2019

I hope it's the SMS7621-079LF version, SC-79, 0.2pF.

On 3 May 2019 13:09:25 -0700, Winfield Hill wrote:

We originally used the SC79, but they didn't solder well. Kept popping off boards. Now we use the SOD323, aka BAT15-03W, about the same capacitance.

I tried the 4-diode dual doubler and it works (in Spice) great.

Version 4 SHEET 1 880 680 WIRE 128 -128 80 -128 WIRE 160 -128 128 -128 WIRE 256 -128 224 -128 WIRE 304 -128 256 -128 WIRE 384 -128 304 -128 WIRE 512 -128 448 -128 WIRE 304 -80 304 -128 WIRE 80 -64 80 -128 WIRE 32 -48 -32 -48 WIRE 304 32 304 -16 WIRE 32 48 32 0 WIRE 80 48 80 16 WIRE 80 48 32 48 WIRE 80 80 80 48 WIRE -304 96 -576 96 WIRE -96 128 -160 128 WIRE -32 128 -32 -48 WIRE -32 128 -96 128 WIRE 160 128 -32 128 WIRE 256 128 224 128 WIRE 304 128 256 128 WIRE 384 128 304 128 WIRE 512 128 512 -128 WIRE 512 128 448 128 WIRE 624 128 512 128 WIRE 656 128 624 128 WIRE -304 160 -464 160 WIRE 512 160 512 128 WIRE 656 160 656 128 WIRE -576 176 -576 96 WIRE -464 176 -464 160 WIRE 304 176 304 128 WIRE 304 288 304 240 WIRE 512 288 512 240 WIRE 656 288 656 224 WIRE -576 320 -576 256 WIRE -464 320 -464 256 FLAG 304 288 0 FLAG 512 288 0 FLAG 656 288 0 FLAG -96 128 ECL+ FLAG 624 128 OUT FLAG -576 320 0 FLAG -464 320 0 FLAG 304 32 0 FLAG 80 80 0 FLAG 256 -128 M1 FLAG 256 128 M2 FLAG 128 -128 ECL- SYMBOL diode 320 240 R180 WINDOW 0 -45 25 Left 2 WINDOW 3 -41 -4 Left 2 SYMATTR InstName D1 SYMATTR Value Ds SYMBOL diode 384 144 R270 WINDOW 0 -40 35 VTop 2 WINDOW 3 -46 32 VBottom 2 SYMATTR InstName D2 SYMATTR Value Ds SYMBOL res 496 144 R0 WINDOW 0 60 46 Left 2 WINDOW 3 49 78 Left 2 SYMATTR InstName R1 SYMATTR Value 100K SYMBOL cap 640 160 R0 WINDOW 0 61 20 Left 2 WINDOW 3 53 57 Left 2 SYMATTR InstName C1 SYMATTR Value 100p SYMBOL cap 224 112 R90 WINDOW 0 80 31 VBottom 2 WINDOW 3 87 32 VTop 2 SYMATTR InstName C2 SYMATTR Value 5p SYMBOL SpecialFunctions\\modulate -304 96 R0 WINDOW 0 45 -55 Left 2 WINDOW 3 -46 -93 Left 2 SYMATTR InstName A1 SYMATTR Value mark=10Meg space=0 SYMBOL voltage -576 160 R0 WINDOW 0 -93 89 Left 2 WINDOW 3 -280 129 Left 2 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value PULSE(0 1 0 200u 0 1) SYMBOL voltage -464 160 R0 WINDOW 0 68 56 Left 2 WINDOW 3 54 88 Left 2 SYMATTR InstName V1 SYMATTR Value 0.75 SYMBOL diode 320 -16 R180 WINDOW 0 -45 25 Left 2 WINDOW 3 -41 -4 Left 2 SYMATTR InstName D3 SYMATTR Value Ds SYMBOL diode 384 -112 R270 WINDOW 0 -40 39 VTop 2 WINDOW 3 -48 38 VBottom 2 SYMATTR InstName D4 SYMATTR Value Ds SYMBOL cap 224 -144 R90 WINDOW 0 78 30 VBottom 2 WINDOW 3 87 32 VTop 2 SYMATTR InstName C3 SYMATTR Value 5p SYMBOL e 80 -80 R0 WINDOW 0 32 92 Left 2 WINDOW 3 28 119 Left 2 SYMATTR InstName E1 SYMATTR Value -1 TEXT -400 320 Left 2 !.MODEL Ds D(IS=130n RS=4.5 N=1.08 XTI=1.8 EG=.68\n+ CJO=260f M=.047 VJ=.11 FC=.5 BV=4 IBV=10U TT=25p) TEXT -600 24 Left 2 !.tran 100u TEXT -712 -80 Left 2 ;SMS7621 Dual Doubler Detector TEXT -624 -32 Left 2 ;JL May 3 2019

Gosh, this RF stuff is easy.