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lock-in amplifier

If they're just photoconductors, you have to build up enough photocarriers to get a decent ON resistance. To reduce the amount of light required, you want a long carrier lifetime (which is easy to get in silicon, of course) but then you have to wait for them to recombine.

Photoconductors also have twice full shot noise in the photocurrent portion--both the generation and recombination are stochastic. (The literature insists on making this somehow special by calling it 'GR noise' but the physics are pretty much the same as shot noise.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 USA 
+1 845 480 2058 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs
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Everyone has been calling them "FET's". Maybe they really are "photoconductors", some other semiconductor equivalent to CdS?? ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| Phoenix, Arizona  85048    Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Dunno. Nobody else has used silicon photoconductors in yonks, so maybe Marketing decided to make it simpler for folks. Or maybe they work in a completely different way. (My money is on their being a silicon version of a Vactrol.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 USA 
+1 845 480 2058 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

I wonder if Thompson is (still) smart enough to look at voltage:current curves and tell a resistor from a fet?

formatting link 

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators
Reply to
John Larkin

so

CdS makes for nice audio AGC >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| Phoenix, Arizona  85048    Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

so

I think that photoconductors saturate like that too--there's a maximum accessible drift rate, and a finite supply of carriers. Polycrystalline CdS is a much crappier material.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 USA 
+1 845 480 2058 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

so

curves

Yep. Someone needs to tell Ol' Bird Brain that the only difference is the gate control. I still puzzle over why Larkin has to continue this asshole behavior. Will he ever grow up? ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| Phoenix, Arizona  85048    Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

they

obvious

There

so

curves

Please leave me out of the flame war. I'm interested in technical topics far more than in personalities.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 USA 
+1 845 480 2058 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

hey

ous

ere

.

nk so

        ...Jim Thompson
     ...Jim Thompson

Ahh, (a light dawns) you've mentioned the double shot noise in photoconductors, but I never got it.

I've got this 'weird' dark noise from the reverse biased LED's I've been playing with. I'm pretty sure it's after pulsing of the avalanche. Which they attribute to some sort of traps in the avalnche region. There's an observable 'bunchiness' in the counts.

George H.

(The

t -

Reply to
George Herold

they

obvious

There

think so

curves

Same here. But Larkin just _will_not_ let it go :-( ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| Phoenix, Arizona  85048    Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

they

obvious

There

think so

curves

Phil, you have my respect for that, unlike others who prefer to just fling dung (does it remind you of the chariot races at UBC?).

Reply to
Ralph Barone

they

s

vious

There

dV.

hink so

te

n
I
        ...Jim Thompson

This shows up in SPADs - single photon avalanche diodes. The Milan mob have published useful stuff on that subject.

--
Bill Sloman, Sydney
Reply to
Bill Sloman

they

obvious

There

think so

curves

I never went to the chariot races. IIRC they were (a) an engineering thing, and (b) before my time. I heard about them from my big brother, who was in CS but hung out with a bunch of gears. They weren't the most welcoming crowd.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 USA 
+1 845 480 2058 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

they

obvious

There

think so

gate

curves

welcoming crowd.

Weird... I remember them and I'm pretty certain I was there after you. However, I also avoided the chariot race. Entering into a "race to the bottom" just didn't seem like a good idea.

Reply to
Ralph Barone

they

flows

obvious

There

dQ=C.dV.

think so

gate

I

recombine.

curves

welcoming crowd.

I graduated in '81. You?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 USA 
+1 845 480 2058 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

charge they

flows

obvious

There

dQ=C.dV.

think so

gate

I

get

recombine.

curves

welcoming crowd.

1988. EE.
Reply to
Ralph Barone

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