Is there a Spice model of a photo diode that delivers
current ( laser_power, Vbias ...) ??
I'm not yet bound to a certain type. Application is low frequency, but very low noise.
And Phil, some of your papers were a tremendous help!
Cheers, Gerhard
On a sunny day (Wed, 14 Dec 2022 12:29:07 +0100) it happened Gerhard Hoffmann snipped-for-privacy@arcor.de wrote in <tncc23$11oj7$ snipped-for-privacy@solani.org:
Yes burning papers can be a big help now it is freezing and prices have gone up because of the war in Europe triggered by the half senile US ByeThen preCendent and his corrupt criminal drugs addicted son.
A cap in parallel with a current source is usually good enough. Or a current source in parallel with a diode if you expect a lot of voltage swing; that's about what a photodiode is.
Glad you like them. Besides the current source and capacitor that John mentions, you also have to care about the series resistance. Devices that look identical, such as the dice in the BPW34 and SFH206K, can have very different resistances (50 vs 300 ohms in that case).
That resistance adds its Johnson noise to the op amp's voltage noise, which seriously limits how well you can do with bootstrapping.
Hamamatsu has some nice devices, e.g. the S6968, which is a giant lensed thing with about 40 pF of capacitance and only a couple of ohms Rseries.
Cheers
Phil Hobbs
(Currently working on a training seminar for Hamamatsu apps engineers)
The conventional photodiode SPICE model's shown below.
Important standard diode model SPICE parameters:
EG Bandgap IS Saturation current Rs Series resistance of Dfwd diode CJO Zero-bias p-n capacitance M Grading coefficient of p-n junction IS Saturation current N Emission coefficient Rsh Shunt resistance Iph Photocurrent
Pertinent schematic:
Iph is a constant current source, the photocurrent. Rsh Shunt resistance. Derived from +10mV and -10mV with measured current. Determines noise current in photovoltaic mode. Rs Contact and non depleted semiconductor resistance. Determines rise time and the linearity. Cj Junction capacitance. Determines the response speed. Danke,
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