Fast comparators

Hi all, so this will turn my spad pulse into the digital world. I was looking at this page,

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I'm not sure about the output voltage. We may want 5V so I stuck with those. Then I wondered about LVDS. I don't think I want this either. Unless you're 'allowed' to hook it up single ended. After that I'd like something as fast as possible, because I might end needing it for a fast quench circuit.

I've got the LT1016 in stock (10 ns), then there are a bunch with ~4ns, I guess I'll order some of the LT1711's, but I'd be happy to hear other suggestions.

George H.

Reply to
George Herold
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An LVDS-to-TTL line receiver, like the DS90LV012, makes a pretty good, very fast RRIO comparator. For 40 cents. The DC offset specs aren't as good as an official comparator.

The ADCMP600 series looks good. 3.5 ns, RRIO, programmable hysteresis.

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John Larkin         Highland Technology, Inc 
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John Larkin

+1. You probably don't need super accurate voltage discrimination for a SPAD breakdown event. ;)

I've had good luck with the FIN1002 and FIN1018, about 20 cents in reels.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Phil Hobbs

100ns is called high speed these days?
Reply to
Tom Del Rosso

My fave comparator in that class is the LM319. Dead useful.

The FIN10xx parts are about 300 ps.

Cheers

Phil Hobbs

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Phil Hobbs

Yeah but you can feed a family in Africa with its pin count and power consumption...

Partial to MCP6561/2 myself, assuming you don't need the 30V.

Tim

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Tim Williams

Right, with the R_sense value I can trade off amplitude and speed. I think, I need to take more data. There will be two detectors, so I really care more about jitter (delta_t) than t.

Cost is irrelevant, the detector is $250 for one, maybe $100 for 100.

I thought we had lt1016 in stock, but I was wrong. I ordered that and lt1711s (5ns) today. Maybe I should relax on 5V and go faster at 3V?

George H.

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George Herold

Don't ask me, I searched for high speed comparators. George H.

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George Herold

I don't have a physical family in Africa, though I do help support a missionary there. She's doing great work in Uganda, and it goes both ways--I've been profoundly grateful for many Africans' missionary work over here, especially Abp Henry Luke Orombi of Uganda, who has done great things for me and mine personally, and Bp. John Rucyahana of Shyira in Rwanda, whom I've been privileged to have met a couple of times. Bp. John is rightly admired for his heroic work during the genocide.

Bp. John visited our church in the mid '90s, after things had calmed down a bit there, and asked for someone who could write to come and be his driver for a year and write his story. I wanted very much to do that, but as I was blessed with a young family, it wasn't my place. Fortunately someone else did it:

The lowish quiescent current is nice, and Microchip historically has been very good about keeping parts in production, but 6.5V abs max is a crummy trade for 50 ns speed. Accepting a 6.5v abs max VCC, you can do a lot better, but for higher voltage the 319 is the bomb.

Cheers

Phil Hobbs

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Phil Hobbs

We use FIN1101 (lvds-to-lvds buffer) as a comparator, driving its lvds output into an FPGA diff input. The 1101 prop delay is about 1 ns.

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John Larkin         Highland Technology, Inc 

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John Larkin

oking

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The one I recognised, and have used, was the AD96685. Sergio Cova used some thing like it in one of his SPAD set-ups, and he exploited the fast input l atch feature that was introduced in the Am685 and widely copied by other ma nufacturers. I exploited it back in 1978

Sloman, A.W. and Swords, M.D. "A fast and economical gated discriminator", Journal of Physics E: Scientific Instruments, 11, 521-524 (1978).

but Sergio Cova used it much better.

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Bill Sloman, Sydney
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bill.sloman

I'm not sure about the output voltage. We may want 5V so I stuck with those.

Thanks, that's interesting.

So that one is more'single supply' rather than 'RRIO'. Some 'RRIO' op amps have big offset shifts within a couple of volts of VDD as well, though 50 mV is a lot.

Cheers

Phil Hobbs

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Phil Hobbs

Hey, what do you want for 20 cents? We use it in cheap fast timing ramps, and apply a polynomial calibration to the DAC data and don't run quite all the way to Vcc. My kids can whip out Python code fast.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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John Larkin

I meant that in the sense of, ahh... Alan Sherman was it? Something old and corny like that.

But that's cool too. :)

Tim

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Seven Transistor Labs, LLC 
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Tim Williams

Oh big whoop, they've been doing those for years...

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:^) A rather neat device, characteristics much cleaner than, say, a dual gate MOSFET. Just that, well... all the problems that tubes have: higher voltages (input and especially bias), high capacitances, low output current, and having a heater.

Tim

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Seven Transistor Labs, LLC 
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Reply to
Tim Williams

I'm not sure about the output voltage. We may want 5V so I stuck with

Thanks, that's interesting.

The world, obviously. ;)

Yup. DFH is good like that too.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Reply to
Phil Hobbs

yer kidding. ;)

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Phil Hobbs

I don't have the time or the people skills to do that sort of thing, but I can write checks. This is one of the better charities in terms of benefits per buck:

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I've funded fixing almost 100 leaky ladies so far.

All our employees are encouraged to suggest donation targets. It makes people happy to do stuff like this, and nobody seems to resent the theoretical tradeoff against salaries and bonuses.

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
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John Larkin

And of course those of us with LLCs can still deduct charitable donations. (LLCs and charitable donations are both highly recommended.)

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Phil Hobbs

We're a C corp, and up to 10% of our profit can be donated and expensed. I make my donations through the corp.

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
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John Larkin

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