# How to emulate photo diode behaviour

Background:

My photo diode is here Characteristics are PW 10ns-150ns, PRF - 1Hz-1Khz, current output 10nA-100mA

i have selected a TIA for processing the above signal to an extent, by using LT spice simulator i was able to simulate the IC and its behavior and checked the performance to an extent.

but i want to emulate the photo diode behavior so that i can feed a signal similar to photo diode to my read out circuit

Problem statement:

in short i want to know how can i create a current source, in fact a pulsating current source with above characteristics,

What i want to try :

to solve the problem i have decided to go with a voltage source like this, what if i place a series resistor between TIA input and voltage source, by tweaking the series resistor wont i be able to change the current to the TIA ? am in the right direction ?? is there any alternate approach to create a current source having above characteristics ?

EDIT:

Any way due to opamp saturation at maximum the current can only go to vcc/rf which is 2.5V / 1K= 2.5mA

Please observe that the circuit shown is meant only to showcase what am i trying.

simulate this circuit – Schematic created using CircuitLab

EDIT 2:

I want to generate a minimum current of 30uA and maximum 2.5mA with above pulse characteristics, The voltage source is a positive polarity one, while i have negative polarity supply also, link to source

As raised by the answers, to clear more on the circuit, the circuit involves a protection diode at opamp input to surge extra current and also protect opamp input from voltage greater than 2V, the TIA is followed by a inverter then a high speed comparator which is a LVDS output having a 100 Ohm termination, that is it !

Something like this :

simulate this circuit

I know few short comings of the circuit, i want measure as much is possible from the circuit,please throw your comments more on creating current source of characteristics discussed in background, if not the above circuit i can experiment with some other, but my main intention in this question is to discuss and come to a conclusion on the best way to create a valid current source

• You don't appear to be learning from your earlier questions. 100 mA through a 1 kohm resistor implies the opamp can produce 100 volt on its output whilst sourcing 100 mA. Do you really think the opamp chosen can do this? – Andy aka Mar 4 '17 at 11:21
• Also, you won't get 100 mA from the photodiode in its linear operating region by a mile. Yes, if you do the math on the absolute max incident power (and effective receive area) it implies a few hundred mA but that assumes the responsivity remains at the normal value at these extremes and it won't. – Andy aka Mar 4 '17 at 11:31
• I understand. The photo current is limited to 2.5mA. But iam more keen in knowing how can i create a current source – kakeh Mar 5 '17 at 7:46
• slightly related noise (photodiode) question: How to estimate minimum detectable light pulse in a photodiode (5 ms, 44 kHz modulated)? any thoughts? – uhoh Jan 22 at 2:02