Photodiode SPICE models?

Been there myself but ran out of time and did the design sans sims ... rummaging in some old notes ... ah, here, in case you have library access:

Ravezzi L.; Dalla Betta G.-F.1; Stoppa D.; Simoni A., Microelectronics Journal, Vol.31, No.4, April 2000, pp. 277-282, Elsevier.

Sorry, I wish I had it but I don't. But these are available online:

Ecole Polytechnique in France has developed a model a couple years ago, you might want to contact: razvan.negru polytechnique edu

Specialty stuff but may be helpful:

Thanks, Joerg. I'll do that.

Cheers

Phil Hobbs

I've used this model several years ago (MRD500 photodiode):

--- model starts here ------------------------

• PSpice Model Editor - Version 10.5.0

*$

• A = Anode

• C = Cathode

• P = (light)Power as voltage input .SUBCKT MRD500 A C P PARAMS: Spec=1.0 Sensy=0.3894

• MRD500 from Motorola * RAP 7/97 DPD A C PhotoDet RDUMMY P 0 1G GPD C A TABLE {V(P)* Spec * Sensy} (0,0) (1,1) .MODEL PhotoDet D IS=1.02p RS=10 N=0.841978 BV=100 IBV=1u

• CJO=6.03p VJ=0.202968 M=0.146605 TT=1n ISR=17p .ends

--- end of model ------------------------------

Let me know if you need it as OrCAD library file.

Yuri.

Phil,

Unfortunately, transient and DC simulations won't/don't show noise.

A .AC analysis should show noise. I don't know the set-ups for LTspice.

.MODEL PhotoDet is likely lacking in noise coefficients, so it's defaulting to who knows what. ...Jim Thompson

Jim,

Thanks. I should have been clearer I expect--I'm trying to do a .noise simulation, and I see the diode noise but it's anywhere from 1% to 75% of the correct shot noise value depending on the device and the value of Iphoto. Replacing the diode with a 1N5817 gets nearly the right answer at 1 mA but is hopelessly low at 1 uA. Using a diode-connected BFT25A (B-C shorted) gives results about 10 dB too low at all photocurrents.

I saw this exact technique recommended in a paper. There's obviously something I'm doing wrong, but I don't know what it is.

Cheers

Phil Hobbs

Ah, I see where the confusion arose--I'm not using Yuri's circuit, but the one I attached. Here it is again inline.

Still weird.

Cheers

Phil

--------- ShotNoiseGen.asc ------------------- Version 4 SHEET 1 880 732 WIRE 80 32 16 32 WIRE 160 32 80 32 WIRE 400 32 288 32 WIRE 16 48 16 32 WIRE 160 48 160 32 WIRE 80 64 80 32 WIRE 400 64 400 32 WIRE 288 96 288 32 WIRE 160 128 160 112 WIRE 16 160 16 128 WIRE 80 160 80 128 WIRE 288 208 288 176 WIRE 400 208 400 144 WIRE 400 208 288 208 FLAG 16 160 0 FLAG 400 32 Output FLAG 80 160 0 FLAG 160 208 0 FLAG 288 208 0 SYMBOL res 384 48 R0 SYMATTR InstName R1 SYMATTR Value 10k SYMBOL current 16 128 R180 WINDOW 0 24 88 Left 0 WINDOW 3 24 0 Left 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName I1 SYMATTR Value {Iphoto} SYMBOL voltage 160 112 R0 WINDOW 123 0 0 Left 0 WINDOW 39 24 118 Left 0 SYMATTR SpiceLine Rser=0 SYMATTR InstName V2 SYMATTR Value 0 SYMBOL cap 144 48 R0 SYMATTR InstName C2 SYMATTR Value 1G SYMATTR SpiceLine Rser=1f Lser=1f Rpar=1T SYMBOL bi2 288 176 M180 WINDOW 0 24 88 Left 0 WINDOW 3 24 0 Left 0 SYMATTR InstName B2 SYMATTR Value I=Iphoto+I(V2) SYMBOL diode 64 64 R0 SYMATTR InstName D1 SYMATTR Value Dshot TEXT -216 128 Left 0 !.param Iphoto=1m TEXT -216 160 Left 0 !.noise V(Output) I1 dec 10 1 1g TEXT -200 104 Left 0 !.model Dshot D()

Phil, this is most likely a stupid idea, but does model have the correct source impedance for the 'diode as shot noise source'. R =3D kT/ (eI)

(I loved the 'link' that I clicked on an it loaded the whole schematic.. cute)

George H.

Hmm. That's an interesting point...perhaps the diode models aren't implemented the way I thought, with the shot noise being a current source internally.

LTSpice rides again--flat ASCII schematic files. Go, Mike!

Cheers

Phil Hobbs

any

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below

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=3D kT/

Excellent! Now you've got something with the correct impedance. I was 'burned' by the diode impedance when I first tried to measure the shot noise from a diode. I biased it with a battery and large resistor and fed the bottom end into a TIA opamp. NO noise??? (well except for opamp and resistor noise.) I had to add a capacitor to allow for a low impedance path for the shot noise.

Funny, how you usually have to screw something up before you really learn it.

George H.