PIN Photodiode: needs biasing?

Discussion in 'Electronic Design' started by Robert Scott, Mar 12, 2007.

  1. Robert Scott

    Robert Scott Guest

    I have been doing some experimenting with a transimpedance amp (LF353) and a PIN
    photodiode. So far I have been using only a simple 1M feedback resistor with
    zero bias on the diode. Then I noticed in the datasheet for the PIN photodiode
    (NEC PH302) it shows a graph of photodiode current as a function of reverse
    bias. According to that graph, the photodiode current should be about double
    with 2 volts of reverse bias on the diode as compared with zero bias. When I
    tried it, the gain of the system remained the same (I have a squarewave light
    signal generated by a LED). It did improve the transient response quite a bit,
    especially when I rasied the bias to 7 volts (due to the reduced diode
    capacitance, I guess) but I saw no evidence of increased photodiode current. Is
    this bogus? I have not seen this stated anywhere else besides the NEC PH302
    datasheet, but Graeme in his classic book on Photodiode Amplifiers does say that
    PIN diodes are usually used with bias. Why is that? Why PINs and not all
    photodiodes?


    Robert Scott
    Ypsilanti, Michigan
     
    Robert Scott, Mar 12, 2007
    #1
    1. Advertising

  2. "Robert Scott" <---@---> schrieb im Newsbeitrag
    news:...
    >I have been doing some experimenting with a transimpedance amp (LF353) and
    >a PIN
    > photodiode. So far I have been using only a simple 1M feedback resistor
    > with
    > zero bias on the diode. Then I noticed in the datasheet for the PIN
    > photodiode
    > (NEC PH302) it shows a graph of photodiode current as a function of
    > reverse
    > bias. According to that graph, the photodiode current should be about
    > double
    > with 2 volts of reverse bias on the diode as compared with zero bias.
    > When I
    > tried it, the gain of the system remained the same (I have a squarewave
    > light
    > signal generated by a LED). It did improve the transient response quite a
    > bit,
    > especially when I rasied the bias to 7 volts (due to the reduced diode
    > capacitance, I guess) but I saw no evidence of increased photodiode
    > current. Is
    > this bogus? I have not seen this stated anywhere else besides the NEC
    > PH302
    > datasheet, but Graeme in his classic book on Photodiode Amplifiers does
    > say that
    > PIN diodes are usually used with bias. Why is that? Why PINs and not all
    > photodiodes?
    >
    >
    > Robert Scott
    > Ypsilanti, Michigan


    Hello Robert,

    The photo current is independent of the reverse voltage at such low
    currents.
    I guess they measured the photo current with an ampere-meter with 100kOhm
    input resistance.

    See figure 3.3 of this application-note.
    http://sales.hamamatsu.com/assets/applications/SSD/photodiode_technical_information.pdf

    Best regards,
    Helmut
     
    Helmut Sennewald, Mar 12, 2007
    #2
    1. Advertising

  3. Robert Scott

    redbelly Guest

    On Mar 12, 3:33 pm, ---@--- (Robert Scott) wrote:
    > I have been doing some experimenting with a transimpedance amp (LF353) and a PIN
    > photodiode. So far I have been using only a simple 1M feedback resistor with
    > zero bias on the diode. Then I noticed in the datasheet for the PIN photodiode
    > (NEC PH302) it shows a graph of photodiode current as a function of reverse
    > bias. According to that graph, the photodiode current should be about double
    > with 2 volts of reverse bias on the diode as compared with zero bias. When I
    > tried it, the gain of the system remained the same (I have a squarewave light
    > signal generated by a LED). It did improve the transient response quite a bit,
    > especially when I rasied the bias to 7 volts (due to the reduced diode
    > capacitance, I guess) but I saw no evidence of increased photodiode current. Is
    > this bogus? I have not seen this stated anywhere else besides the NEC PH302
    > datasheet, but Graeme in his classic book on Photodiode Amplifiers does say that
    > PIN diodes are usually used with bias. Why is that? Why PINs and not all
    > photodiodes?
    >
    > Robert Scott
    > Ypsilanti, Michigan


    Robert,

    What I have noticed with unbiased silicon photodiodes in general is
    that they are pretty linear up to about 0.2 or 0.25 V output, no
    matter what current + load resistor combination is used. By the time
    the output gets up to 0.3 or 0.4 V, the response (output vs. incident
    photo power) is pretty well flattening out. You don't mention what
    output current or voltage you are getting, but hopefully this info
    helps you determine if you should need biasing for linearity.

    That being said, it has been 12+ years since I worked with a PIN
    photodiode, and I'm not sure if they behave vastly different, in terms
    of linearity, vs. a regular PN type. If speed is an issue, then as
    you noticed biasing will help you with that.

    Regards,

    Mark
     
    redbelly, Mar 12, 2007
    #3
  4. Robert Scott

    Joerg Guest

    Robert Scott wrote:
    > I have been doing some experimenting with a transimpedance amp (LF353) and a PIN
    > photodiode. So far I have been using only a simple 1M feedback resistor with
    > zero bias on the diode. Then I noticed in the datasheet for the PIN photodiode
    > (NEC PH302) it shows a graph of photodiode current as a function of reverse
    > bias. According to that graph, the photodiode current should be about double
    > with 2 volts of reverse bias on the diode as compared with zero bias. When I
    > tried it, the gain of the system remained the same (I have a squarewave light
    > signal generated by a LED). It did improve the transient response quite a bit,
    > especially when I rasied the bias to 7 volts (due to the reduced diode
    > capacitance, I guess) but I saw no evidence of increased photodiode current. Is
    > this bogus? I have not seen this stated anywhere else besides the NEC PH302
    > datasheet, but Graeme in his classic book on Photodiode Amplifiers does say that
    > PIN diodes are usually used with bias. Why is that? Why PINs and not all
    > photodiodes?
    >


    Provided you built a good TIA where the voltage at the photodiode node
    does not move the reverse bias is primarily intended to reduce the diode
    capacitance and thus improve speed. It also allows you to reduce the
    compensation cap Cfb for the TIA, making it a bit more hot. But that
    really only matters in the 100MHz+ speed ranges, not so much for an LF
    series amp.

    I finished a photodiode design about a month ago and this one went to
    100MHz. I moved the bias around a bit but even there it didn't matter. I
    just kept it in case the client wants to go higher one day.

    --
    Regards, Joerg

    http://www.analogconsultants.com
     
    Joerg, Mar 12, 2007
    #4
  5. Robert Scott

    John Larkin Guest

    On Mon, 12 Mar 2007 19:33:24 GMT, ---@--- (Robert Scott) wrote:

    >I have been doing some experimenting with a transimpedance amp (LF353) and a PIN
    >photodiode. So far I have been using only a simple 1M feedback resistor with
    >zero bias on the diode. Then I noticed in the datasheet for the PIN photodiode
    >(NEC PH302) it shows a graph of photodiode current as a function of reverse
    >bias. According to that graph, the photodiode current should be about double
    >with 2 volts of reverse bias on the diode as compared with zero bias. When I
    >tried it, the gain of the system remained the same (I have a squarewave light
    >signal generated by a LED). It did improve the transient response quite a bit,
    >especially when I rasied the bias to 7 volts (due to the reduced diode
    >capacitance, I guess) but I saw no evidence of increased photodiode current. Is
    >this bogus? I have not seen this stated anywhere else besides the NEC PH302
    >datasheet, but Graeme in his classic book on Photodiode Amplifiers does say that
    >PIN diodes are usually used with bias. Why is that? Why PINs and not all
    >photodiodes?
    >
    >
    >Robert Scott
    >Ypsilanti, Michigan


    I think current can be lower at zero bias because some photon-smacked
    hole-electron pairs recombine and are lost. With a reverse-bias field,
    they are swept up and collected quickly.

    For the first few volts of reverse bias, junction capacitance drops
    rapidly, so the *circuit* gets faster. That effect flattens out
    quickly, but higher bias sweeps carriers out faster and continues to
    improve *diode* speed.

    At very high voltages (50? 100?) you can get avalanche multiplication
    that greatly increases gain (and noise.) Some diodes are designed to
    do this well.

    Something like that.

    John
     
    John Larkin, Mar 13, 2007
    #5
  6. Robert Scott

    Joerg Guest

    John Larkin wrote:

    > On Mon, 12 Mar 2007 19:33:24 GMT, ---@--- (Robert Scott) wrote:
    >
    >
    >>I have been doing some experimenting with a transimpedance amp (LF353) and a PIN
    >>photodiode. So far I have been using only a simple 1M feedback resistor with
    >>zero bias on the diode. Then I noticed in the datasheet for the PIN photodiode
    >>(NEC PH302) it shows a graph of photodiode current as a function of reverse
    >>bias. According to that graph, the photodiode current should be about double
    >>with 2 volts of reverse bias on the diode as compared with zero bias. When I
    >>tried it, the gain of the system remained the same (I have a squarewave light
    >>signal generated by a LED). It did improve the transient response quite a bit,
    >>especially when I rasied the bias to 7 volts (due to the reduced diode
    >>capacitance, I guess) but I saw no evidence of increased photodiode current. Is
    >>this bogus? I have not seen this stated anywhere else besides the NEC PH302
    >>datasheet, but Graeme in his classic book on Photodiode Amplifiers does say that
    >>PIN diodes are usually used with bias. Why is that? Why PINs and not all
    >>photodiodes?
    >>
    >>
    >>Robert Scott
    >>Ypsilanti, Michigan

    >
    >
    > I think current can be lower at zero bias because some photon-smacked
    > hole-electron pairs recombine and are lost. With a reverse-bias field,
    > they are swept up and collected quickly.
    >
    > For the first few volts of reverse bias, junction capacitance drops
    > rapidly, so the *circuit* gets faster. That effect flattens out
    > quickly, but higher bias sweeps carriers out faster and continues to
    > improve *diode* speed.
    >
    > At very high voltages (50? 100?) you can get avalanche multiplication
    > that greatly increases gain (and noise.) Some diodes are designed to
    > do this well.
    >


    Just be aware that some of the communications diodes cannot tolerate
    more than 5V. At least per abs max in the datasheet.

    --
    Regards, Joerg

    http://www.analogconsultants.com
     
    Joerg, Mar 13, 2007
    #6
  7. Robert Scott

    Guest

    On Mar 12, 12:33 pm, ---@--- (Robert Scott) wrote:
    > I have been doing some experimenting with a transimpedance amp (LF353) and a PIN
    > photodiode. So far I have been using only a simple 1M feedback resistor with
    > zero bias on the diode. Then I noticed in the datasheet for the PIN photodiode
    > (NEC PH302) it shows a graph of photodiode current as a function of reverse
    > bias. According to that graph, the photodiode current should be about double
    > with 2 volts of reverse bias on the diode as compared with zero bias. When I
    > tried it, the gain of the system remained the same (I have a squarewave light
    > signal generated by a LED). It did improve the transient response quite a bit,
    > especially when I rasied the bias to 7 volts (due to the reduced diode
    > capacitance, I guess) but I saw no evidence of increased photodiode current. Is
    > this bogus? I have not seen this stated anywhere else besides the NEC PH302
    > datasheet, but Graeme in his classic book on Photodiode Amplifiers does say that
    > PIN diodes are usually used with bias. Why is that? Why PINs and not all
    > photodiodes?
    >
    > Robert Scott
    > Ypsilanti, Michigan


    The datasheet I found doesn't start at zero. Do you have a link?
     
    , Mar 13, 2007
    #7
  8. Robert Scott

    Guest

    On Mar 12, 12:33 pm, ---@--- (Robert Scott) wrote:
    > I have been doing some experimenting with a transimpedance amp (LF353) and a PIN
    > photodiode. So far I have been using only a simple 1M feedback resistor with
    > zero bias on the diode. Then I noticed in the datasheet for the PIN photodiode
    > (NEC PH302) it shows a graph of photodiode current as a function of reverse
    > bias. According to that graph, the photodiode current should be about double
    > with 2 volts of reverse bias on the diode as compared with zero bias. When I
    > tried it, the gain of the system remained the same (I have a squarewave light
    > signal generated by a LED). It did improve the transient response quite a bit,
    > especially when I rasied the bias to 7 volts (due to the reduced diode
    > capacitance, I guess) but I saw no evidence of increased photodiode current. Is
    > this bogus? I have not seen this stated anywhere else besides the NEC PH302
    > datasheet, but Graeme in his classic book on Photodiode Amplifiers does say that
    > PIN diodes are usually used with bias. Why is that? Why PINs and not all
    > photodiodes?
    >
    > Robert Scott
    > Ypsilanti, Michigan


    The datasheet I found doesn't start at zero. Do you have a link?
     
    , Mar 13, 2007
    #8
  9. Robert Scott

    Robert Scott Guest

    On 12 Mar 2007 20:41:26 -0700, wrote:

    >
    >The datasheet I found doesn't start at zero. Do you have a link?
    >


    www.datasheetarchive.com/datasheet.php?article=2695045

    It is a crummy optically-scanned image document. Do you have a better one,
    perhaps one that is not just an optical scan?


    Robert Scott
    Ypsilanti, Michigan
     
    Robert Scott, Mar 13, 2007
    #9
  10. Robert Scott

    Guest

    On Mar 13, 4:44 am, ---@--- (Robert Scott) wrote:
    > On 12 Mar 2007 20:41:26 -0700, wrote:
    >
    >
    >
    > >The datasheet I found doesn't start at zero. Do you have a link?

    >
    > www.datasheetarchive.com/datasheet.php?article=2695045
    >
    > It is a crummy optically-scanned image document. Do you have a better one,
    > perhaps one that is not just an optical scan?
    >
    > Robert Scott
    > Ypsilanti, Michigan


    That is the same one I found. Since the graph doesn't go to zero, how
    did you conclude the shift for 2v back bias?
     
    , Mar 13, 2007
    #10
  11. <> schrieb im Newsbeitrag
    news:...
    > On Mar 13, 4:44 am, ---@--- (Robert Scott) wrote:
    >> On 12 Mar 2007 20:41:26 -0700, wrote:
    >>
    >>
    >>
    >> >The datasheet I found doesn't start at zero. Do you have a link?

    >>
    >> www.datasheetarchive.com/datasheet.php?article=2695045
    >>
    >> It is a crummy optically-scanned image document. Do you have a better
    >> one,
    >> perhaps one that is not just an optical scan?
    >>
    >> Robert Scott
    >> Ypsilanti, Michigan

    >
    > That is the same one I found. Since the graph doesn't go to zero, how
    > did you conclude the shift for 2v back bias?


    Hello miso,

    They obviously measured with an ampere-meter with 100kOhm input resistance.
    This is nonsense of course in a photo-diode application when you measure
    over a
    wide range of light(photo current). As soon as there is a voltage drop of a
    very few 100mV on the load resistor, the measured current isn't correct
    because
    the photo diode gets internally forward biased by this value. Either a
    negative bias
    voltage will help to prevent that or a short circuit current measurement
    (transimpedance amplifier).

    Best regards,
    Helmut
     
    Helmut Sennewald, Mar 13, 2007
    #11
  12. Robert Scott

    redbelly Guest

    On Mar 13, 3:57 pm, wrote:
    > On Mar 13, 4:44 am, ---@--- (Robert Scott) wrote:
    >
    > > On 12 Mar 2007 20:41:26 -0700, wrote:

    >
    > > >The datasheet I found doesn't start at zero. Do you have a link?

    >
    > >www.datasheetarchive.com/datasheet.php?article=2695045

    >
    > > It is a crummy optically-scanned image document. Do you have a better one,
    > > perhaps one that is not just an optical scan?

    >
    > > Robert Scott
    > > Ypsilanti, Michigan

    >
    > That is the same one I found. Since the graph doesn't go to zero, how
    > did you conclude the shift for 2v back bias?


    Robert is talking about the photocurrent (bottom of p. 3 in the .pdf
    file), whereas you seem to be talking about the graph of leak current
    (top of p. 3).

    Mark
     
    redbelly, Mar 18, 2007
    #12
  13. Robert Scott

    Guest

    On Mar 18, 7:23 am, "redbelly" <> wrote:
    > On Mar 13, 3:57 pm, wrote:
    >
    >
    >
    > > On Mar 13, 4:44 am, ---@--- (Robert Scott) wrote:

    >
    > > > On 12 Mar 2007 20:41:26 -0700, wrote:

    >
    > > > >The datasheet I found doesn't start at zero. Do you have a link?

    >
    > > >www.datasheetarchive.com/datasheet.php?article=2695045

    >
    > > > It is a crummy optically-scanned image document. Do you have a better one,
    > > > perhaps one that is not just an optical scan?

    >
    > > > Robert Scott
    > > > Ypsilanti, Michigan

    >
    > > That is the same one I found. Since the graph doesn't go to zero, how
    > > did you conclude the shift for 2v back bias?

    >
    > Robert is talking about the photocurrent (bottom of p. 3 in the .pdf
    > file), whereas you seem to be talking about the graph of leak current
    > (top of p. 3).
    >
    > Mark


    Does this mean the efficiency of the detector increases with bias? Or
    are they lumping leakage in with photocurrent?
     
    , Mar 18, 2007
    #13
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Boki

    RS232 pin.4 and pin.8

    Boki, Oct 7, 2004, in forum: Electronic Basics
    Replies:
    3
    Views:
    442
  2. MNQ

    PIN Photodiode

    MNQ, Nov 7, 2003, in forum: Electronic Design
    Replies:
    0
    Views:
    276
  3. Haris
    Replies:
    1
    Views:
    1,492
    Spehro Pefhany
    Sep 27, 2004
  4. Roman D. Sinjuk

    PIN photodiode & TIA question

    Roman D. Sinjuk, Sep 17, 2005, in forum: Electronic Design
    Replies:
    1
    Views:
    852
    Phil Hobbs
    Sep 17, 2005
  5. usefulfacts
    Replies:
    0
    Views:
    988
    usefulfacts
    May 31, 2007
Loading...

Share This Page