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SPICE photodiode model--how to put in reverse transit time?

Hi, all,

A Merry Christmas, first of all.

Now that the important stuff is out of the way, I've been thinking about photodiode models.

Photodiode speed is a fairly strong function of reverse bias, and many types of PIN PDs speed up amazingly when you crank up the bias that last little bit (often above the datasheet V_B) to fully deplete the bulk.

Other types are dominated by diffusion in the epi layer, which is too highly doped to be depleted before the device turns to lava.

The diffusion-dominated rise time goes quadratically with diameter, just like the RC rise time, but is typically slower, at least in red-enhanced devices with thick I layers.

The SPICE diode model doesn't seem to include a reverse transit time. Any suggestions of how to model reverse transit time effects in photodiodes?

Thanks

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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There's this paper on the subject...

formatting link

IEEE, so I can't retrieve it.

You have to make a subcircuit. I'll E-mail you some papers that I do have. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     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

Thanks, that's both interesting and digestible. (Important feature on Boxing Day.) ;)

I'll have a whack at seeing whether the large-signal reverse recovery accurately predicts the photodiode behaviour, which ideally should be on the low-level injection end of the curve.

The photocarriers are generated throughout the depletion zone at a low rate, which is pretty different from the reverse recovery of an 1N4007.

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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