On Tuesday, November 21, 2017 at 1:25:46 AM UTC+11, Fitzgerald wrote:
> On 11/20/2017 03:04 PM, Phil Hobbs wrote:
> > It's not uncommon when using a slowish amplifier (60 MHz @ min stable
> > gain, 625 V/us) with a much faster transducer. The op amp can't control
> > its summing junction adequately in the inverting configuration in that
> > case, leading to measurement nonlinearity.
> >
> > Also the MPPC's output is far from shot noise limited (due to the high
> > gain and fixed charge per segment), so you don't care much about the
> > Johnson noise of the load resistor (probably 50 ohms).
> >
> > If you want a fixed, finite integration time, I recommend using
> > ping-pong gated integrators. Each one integrates maybe 60% of the time,
> > and you overlap the two so that at least one is integrating at all
> > times. You can make them closer to 50% duty cycle if you like, but you
> > run the risk of missing stuff if you have both switches transitioning
> > simultaneously, i.e. at exactly 50% duty cycle each.
> >
> > Cheers
> >
> > Phil Hobbs
> >
>
> Thanks! I was thinking about integrating short intervals (10-40 ns) and
> then summing in software if I needed longer integration times.
>
> I like the idea of a ping-pong integrator, but I don't understand why I
> should overlap their integration periods.
Perhaps the devices take a finite time to move from integrating to non-integrating, and you want to put half the signal that lies on a transition into the earlier interval, and the other half into the later interval.
> I would assume that this would
> lead to blurring of consecutive samples.
A finite transition time from integrating to not integrating will have that effect too.
> Wouldn't it be better to have
> the integrator be high-Z on its input when it is not integrating? Any
> charge being generated will just accumulate during the dead-time between
> the ping-pong when both integrators are off.
Perhaps, if it works that way. Summing junctions that move away from the default voltage can do odd things.
--
Bill Sloman, Sydney
Reply by Phil Hobbs●November 20, 20172017-11-20
On 11/20/2017 10:39 AM, George Herold wrote:
> On Monday, November 20, 2017 at 9:04:57 AM UTC-5, Phil Hobbs wrote:
>> On 11/20/2017 08:42 AM, Fitzgerald wrote:
>>> I'm looking into low-light detection using MPPC's and I am testing using
>>> the Hamamatsu C12332-01 evaluation module. I am looking for general
>>> hints, tips and tricks to maximize the performance of these modules.
>>>
>>> We'd like to have a measure for the total amount of photons collected
>>> every 20-100ns (exact timing t.b.d.)
>>>
>>> One of the things that surprised me was that the frontend of the
>>> evaluation board uses an OPA846 in a non-inverting (voltage) amplifier
>>> configuration; and not as a transimpedance amplifier. What would be the
>>> benefit of that?
>>>
>>> Thanks!
>>
>> It's not uncommon when using a slowish amplifier (60 MHz @ min stable
>> gain, 625 V/us) with a much faster transducer.
> Slowish? http://www.ti.com/lit/ds/sbos250e/sbos250e.pdf
> maybe you just typed wrong, the above says 400 MHz at a gain of 10.
>
> George H.
Ah, okay, assumed that the 400 MHz number was the GBW. Still way too
slow to be safe as an inverting TIA with a MPPC.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.nethttps://hobbs-eo.com
Reply by George Herold●November 20, 20172017-11-20
On Monday, November 20, 2017 at 9:04:57 AM UTC-5, Phil Hobbs wrote:
> On 11/20/2017 08:42 AM, Fitzgerald wrote:
> > I'm looking into low-light detection using MPPC's and I am testing using
> > the Hamamatsu C12332-01 evaluation module. I am looking for general
> > hints, tips and tricks to maximize the performance of these modules.
> >
> > We'd like to have a measure for the total amount of photons collected
> > every 20-100ns (exact timing t.b.d.)
> >
> > One of the things that surprised me was that the frontend of the
> > evaluation board uses an OPA846 in a non-inverting (voltage) amplifier
> > configuration; and not as a transimpedance amplifier. What would be the
> > benefit of that?
> >
> > Thanks!
>
> It's not uncommon when using a slowish amplifier (60 MHz @ min stable
> gain, 625 V/us) with a much faster transducer.
> its summing junction adequately in the inverting configuration in that
> case, leading to measurement nonlinearity.
>
> Also the MPPC's output is far from shot noise limited (due to the high
> gain and fixed charge per segment), so you don't care much about the
> Johnson noise of the load resistor (probably 50 ohms).
>
> If you want a fixed, finite integration time, I recommend using
> ping-pong gated integrators. Each one integrates maybe 60% of the time,
> and you overlap the two so that at least one is integrating at all
> times. You can make them closer to 50% duty cycle if you like, but you
> run the risk of missing stuff if you have both switches transitioning
> simultaneously, i.e. at exactly 50% duty cycle each.
>
> Cheers
>
> Phil Hobbs
>
> --
> Dr Philip C D Hobbs
> Principal Consultant
> ElectroOptical Innovations LLC / Hobbs ElectroOptics
> Optics, Electro-optics, Photonics, Analog Electronics
> Briarcliff Manor NY 10510
>
> http://electrooptical.net
> https://hobbs-eo.com
Reply by Fitzgerald●November 20, 20172017-11-20
On 11/20/2017 03:04 PM, Phil Hobbs wrote:
> It's not uncommon when using a slowish amplifier (60 MHz @ min stable
> gain, 625 V/us) with a much faster transducer. The op amp can't control
> its summing junction adequately in the inverting configuration in that
> case, leading to measurement nonlinearity.
>
> Also the MPPC's output is far from shot noise limited (due to the high
> gain and fixed charge per segment), so you don't care much about the
> Johnson noise of the load resistor (probably 50 ohms).
>
> If you want a fixed, finite integration time, I recommend using
> ping-pong gated integrators. Each one integrates maybe 60% of the time,
> and you overlap the two so that at least one is integrating at all
> times. You can make them closer to 50% duty cycle if you like, but you
> run the risk of missing stuff if you have both switches transitioning
> simultaneously, i.e. at exactly 50% duty cycle each.
>
> Cheers
>
> Phil Hobbs
>
Thanks! I was thinking about integrating short intervals (10-40 ns) and
then summing in software if I needed longer integration times.
I like the idea of a ping-pong integrator, but I don't understand why I
should overlap their integration periods. I would assume that this would
lead to blurring of consecutive samples. Wouldn't it be better to have
the integrator be high-Z on its input when it is not integrating? Any
charge being generated will just accumulate during the dead-time between
the ping-pong when both integrators are off.
Reply by Phil Hobbs●November 20, 20172017-11-20
On 11/20/2017 08:42 AM, Fitzgerald wrote:
> I'm looking into low-light detection using MPPC's and I am testing using
> the Hamamatsu C12332-01 evaluation module. I am looking for general
> hints, tips and tricks to maximize the performance of these modules.
>
> We'd like to have a measure for the total amount of photons collected
> every 20-100ns (exact timing t.b.d.)
>
> One of the things that surprised me was that the frontend of the
> evaluation board uses an OPA846 in a non-inverting (voltage) amplifier
> configuration; and not as a transimpedance amplifier. What would be the
> benefit of that?
>
> Thanks!
It's not uncommon when using a slowish amplifier (60 MHz @ min stable
gain, 625 V/us) with a much faster transducer. The op amp can't control
its summing junction adequately in the inverting configuration in that
case, leading to measurement nonlinearity.
Also the MPPC's output is far from shot noise limited (due to the high
gain and fixed charge per segment), so you don't care much about the
Johnson noise of the load resistor (probably 50 ohms).
If you want a fixed, finite integration time, I recommend using
ping-pong gated integrators. Each one integrates maybe 60% of the time,
and you overlap the two so that at least one is integrating at all
times. You can make them closer to 50% duty cycle if you like, but you
run the risk of missing stuff if you have both switches transitioning
simultaneously, i.e. at exactly 50% duty cycle each.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.nethttps://hobbs-eo.com
Reply by Fitzgerald●November 20, 20172017-11-20
I'm looking into low-light detection using MPPC's and I am testing using
the Hamamatsu C12332-01 evaluation module. I am looking for general
hints, tips and tricks to maximize the performance of these modules.
We'd like to have a measure for the total amount of photons collected
every 20-100ns (exact timing t.b.d.)
One of the things that surprised me was that the frontend of the
evaluation board uses an OPA846 in a non-inverting (voltage) amplifier
configuration; and not as a transimpedance amplifier. What would be the
benefit of that?
Thanks!