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How to know opamp burn out? (ad8009)

I am using more than 400 pieces of ad8009 in the circuit. However, it is impossible to determine if the chip is broken. The signal I get experimentally has a 4 V bias voltage. (Output pin) However, the output without a signal has a different bias. Another problem is that there is amps that works normally if i proceed with the next experiment. Circuits incorporate all voltage pins and use + 5 V and - 5 V. 

 

  • Hi, 

    Sorry to hear you're having problems. Could you please attach a schematic?

    Thanks, 

    Kris

  • Hi,

    Before we proceed, you are beyond the operating Output Voltage Range of AD8009 which is only +3.8 V. Some parts might have blown up becuse of overstress.

    Could you give the following values:

    +HV

    R1

    R2
    C1

    What is the amplitude and the width  of the current pulse from the photodiode? Could you give us the part number or the terminal capacitance of the photodiode, please?

    Regards.

    Jino

  • This is our circuit schematic. 

    And this board is made of PCB. 

    For example, an input to 1 C-1 is a small current signal.(photo detector signal)

    We build this signal to be stable and amplified.

    However, some outputs have failed to produce correctly since the test.

    The original signal has a 4 volt bias and has a negative signal.

    (It's the same signal as the picture.)

    But some amps have a - 4 V bias and the signal is not measured.

    Is this a burnt amp?
    However, the operating voltage is measured normally. (+ 5 V, - 5 V)

    Does it mean that the amps is dead when other amps - 4 volts bias is measured?

  • Thank you for the information. Could you reattach your schematic with the photodiode? A picture would do.

  • Thank you for your interest and support.

    +HV  =  +55V (Reverse voltage for pothodiode)

    R1   =   1K

    R2    =  100M
    C1    = 0.1nF

    - amplitude and the width  of the current pulse from the photodiode 

     

    amplitude = about 50mV 

    width = about 50mhz

     

    And the photodiode we use is MPPC array of Hamamatsu. (Here is datasheet /  http://www.hamamatsu.com/resources/pdf/ssd/s13361-3050_series_kapd1054e.pdf )

     

     

    we connected like this.

  • No circuit adds photodiode. Only the input of the amplifier is the cathodes of the photodiode. The above circuit is a circuit used to amplify a photo-diode array per pixel. Anodes just connect to the ground.

  • Hi,

    With all the component values you have in your application, AD8009 couldn't make it. See below:

    1. The AD8009's crossover frequency (fc) at RF = 1 kohms is ~ 180 MHz.

    2. The APD's terminal capacitance in conjunction with RF will make a fp (pole) = 1/ (2pi*RF*Cs). Cs = 320pF, so fp = 497.36 kHz.

    3. We set fx = sqrt (fp * fc), fx = sqrt (497.36k * 180 M) = 9.46 MHz.

    4. Signal Bandwidth can be determined the fz( zero) which is dependent on RF and CF (1/(2pi*RF*CF)). To allow a maximum TIA bandwidth with a 45deg phase margin, let fz = fx. Therefore, CF = 1/ (2pi*9.46 MHz * 1k) = 16.83 pF. Set CF < 16 pF.

    5. In your current design, you are limiting the signal bandwidth to 1.59 MHz. And the input pulse you have, it won't make it.  You can refer on page 30 of ADA4622 datasheet for the details about the computations.

    With that being said, you have to modify your circuit.

    1. Please use AD8099 instead of AD8009. For TIA applications, we want our amplifier to have a high input impedance, so please use Voltage feedback amplifiers.

    2. Use this circuit. With a AD8099, 100 ohms to meet the 20ns requirement. Vout = 50 mA * 100 = 5 Vpp. Set the output Reference (2.5V) such that we are sure that the amplifier is within operating range. Output will swing from +2.5 V to -2.5 V.

    3. These are the responses.

    Hope this helps.

    Regards,

    Jino

  • Thank you very much for your kind response and advice.

    It is so difficult to modify the chip that it is about to change the resistance. 
    It was very helpful.

    Thanks again.

  • Unless I much misunderstand what you are doing, it seems you are not connecting the MPPC (silicon photomultiplier) properly, and I don't see how your hookup can work.  To function, SiPMs need to be biased above their breakdown voltage Vbr, with the addition of an overvoltage Vov to produce the desired gain.  If you are grounding the anode of the device and connecting the cathode to the input you show, then the diode bias will increase after supplies are turned on until the input stage of the amplifier either breaks down or clamps itself, given whatever input protection circuits are internal.  This might be happening at the 4V you mention.  The result is a diode that is not biased sufficiently and an amplifier whose input protection is conducting, therefore the amp is not functional.  The SiPM has to sustain about the 53V you show as applied voltage, give or take, as defined in your data sheet, and then they recommend a nominal 3V Vov.

    The standard ways to do this are to connect the ~55V bias and resistor you show directly to the cathode of the diode, and then connect only the diode anode to the amp input you show; alternatively, one can connect the diode anode to a negative ~55V supply, and the cathode to your input.  The former connection gives negative amp output pulses, the latter positive.  Also it's conventional to place a decoupling cap where the series resistor connects with the diode, to remove noise from the bias supply.

    The Hamamatsu spec sheet you give for your array calls out a Vbr spec of 53 +/- 5V.  I hope this means that they match all the diodes' Vbrs in that array, but that the resulting value can be anywhere between 48 and 58 V.  Then you can use the same supply for all the diodes in one array, but in principle you will have to measure (or Hamamatsu may note) the Vbr for any other arrays you use in your system, and supply a separately set Vbr for each array, also adding whichever Vov you decide to use to each.  Otherwise the gain of each array may differ dramatically from those of the others.

    I have used the AD8009 as a SiPM amplifier; it is a hugely fast part, but the quiescent current is quite high (14mA) and the current noise at the inputs is pretty major.  Depending on your application, you may find that you can trade off some of the speed for much lower power dissipation and quieter operation.  AD 8001 is a wonderful part for this (1mA Iq), as is, for example ( to risk mentioning Brand T's parts on this site), the LMH6723.

  • I should add that I have used, and prefer, the noninverting connection for SiPM amplifiers when using current feedback amps like AD8009 or AD8011 (I meant 8011 in my previous entry, not 8001!).  The advantages are: that the gain of the amplifier can now be chosen freely, whereas the gain in the inverting connection is essentially defined by the feedback resistor, and you can't change this very much without affecting the bandwidth; that the large capacitance of the SiPM (320pF in this case) is not placed directly at the amplifier inverting input, but at the higher -impedance noninverting input, which avoids affecting the closed-loop gain flatness; and that you now no longer are tempted to put the feedback capacitor you show around the feedback resistor.  This last is true because the feedback network is now not affected by the diode capacitance.  You do have to terminate the diode to ground at the noninverting input through some smallish resistance - say 50 Ohms or so.  Another nice characteristic of current feedback amps is that you can tweak their frequency response either up or down by changing the value of the feedback resistor - then change the gain-setting resistor to reestablish the desired gain.