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how to model a pulsed photo diode response

Shyam
Expert 1960 points

I have a photo diode whose response is current output, but not a constant current infact a pulsed current source, but how to model such kind of pulsed current source in TINA


i have seen a pulsed current source in TINA but it has a voltage option which confused me, how can i simulate a current source which  is active for  10ns time and later goes to noise current

kindly throw some light on this

  • 0
    TI__Expert 3555 points

    DARAM,

    This is a very good question. I will start working on providing a solution for you but I have a few questions.

    1. are you using the photo diode in the photo voltaic mode (zero bias) or photo conductive mode (non zero reverse voltage bias)?

    2. do you have the photo diode configured with an amplifier to convert the diode current to voltage?

    3. what is the part number and manufacturer of your photo diode?

    4. with your photo diode, do you know what the noise current is equal to?

  • 0 in reply to Bonnie Baker - WEBENCH Design Center
    Expert 1960 points

    I am really glad for your reply ma'am,

    Let me first explain my situation, my photo diode will recieve laser pulses of width 10-150ns and pulse to pulse gap will be >20us .

    1. photo diode is reverse biased by 12V bias voltage

    2. photo diode current passed to a 50ohm resistor , is where i collect the response from, i am not using any TIA,followed by it can be 2kinds of circuits, one being a amplifier and high speed comparator, other being a peak detector followed by a low speed comparator(for sake of pulse stretching)

    3. http://www.excelitas.com/downloads/dts_harlid.pdf

    4. you can find all details from above datasheet

    currently i am just using a pulsed voltage source and simulating

  • 0 in reply to Shyam
    TI__Expert 3555 points

    Daram,

    Here is your photodiode model, where Ca in the diode's Cathode terminal and An is the diode's Anode terminal. Vbias is the reverse bias across the photodiode which is always a negative voltage (below the Ca voltage). 

    Gpd is a voltage dependent current source.  

    The macromodel that I have generated for TINA is where OPT- is ground and the signal for OPT+ will give you Ampere output = Volts input:

    *****************************************************************
    * Pdiode
    *
    *****************************************************************************
    * (C) Copyright 2016 Texas Instruments Incorporated. All rights reserved.                                           
    *****************************************************************************
    ** This model is designed as an aid for customers of Texas Instruments.
    ** TI and its licensors and suppliers make no warranties, either expressed
    ** or implied, with respect to this model, including the warranties of
    ** merchantability or fitness for a particular purpose.  The model is
    ** provided solely on an "as is" basis.  The entire risk as to its quality
    ** and performance is with the customer.
    *****************************************************************************
    *
    * This model is subject to change without notice. Texas Instruments
    * Incorporated is not responsible for updating this model.
    *
    *****************************************************************************
    *
    ** Released by: WEBENCH
    * Part: Pdiode
    * Date: 7JUN2016
    *
    * Model Version: 1.0
    *
    ***************************************************************
    * The model includes parameters for:                         
    *    1) Depletion (junction) capacitance                       
    *    2) forward/reverse I-V behavior  
    * The model does NOT include parameters for:         
    *    1) Capacitance in forward bias                            
    *    2) Serial Resistance dependency on                   
    *       wavelength/bias/irradiance                             
    *    3) Noise                                                  
    *    4) Intrinsic optical-electrical frequency response
    *         wavelength/bias/irradiance dependency    
    *****************************************************************
    * optical inputs (Opt+, Opt-):                                               
    *    connect voltage source between optical input(+) and       
    *    optical input(-) with voltage representing                
    *    photodiode output current (example 50uV=50uA). Positive current
    *    flows into the cathode node and out the Anode node.                     
    *    For default (no light), set both optical inputs to        
    *    ground (0) = 0VDC   
    ***************************************************************
    * Node Assignments
    *                                   positive optical in
    *                                   |            negative optical in
    *                                   |            |           Cathode
    *                                   |            |           |        Anode
    *                                   |            |           |        |
    *                                   |            |           |        |
    *                                   |            |           |        |
    .subckt Pdiode           Opt+      Opt-     Ca    An

    * Opt+ = optical positive input. Converts voltage to amperes
    * Opt- = optical negative input. Converts voltage to amperes
    * An = Anode of photodiode.
    * Ca = Cathode of photodiode.

    Gpd 2 An Opt+ Opt-  {1}
    D1 An 2 Dpd
    Rs 2 Ca 0.5
    .model Dpd D(Cjo=80p BV=200)

    .ends