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TIPD107: This circuit is suitable at 100 Hz. Is there a way this can be modified to work at around 400 Hz?

Ramish Ashraf
Prodigy 10 points
Part Number: TIPD107
Other Parts Discussed in Thread: INA326,

I want to be able to sense a voltage signal from a photomultiplier tube (in Volts... nominally it would be around 1 V). The voltage signal itself is around 360 Hz. I would like to be able to convert the voltage signal at around 360 Hz into a current signal which can then be read using an electrometer. 

  • 0
    TI__Genius 10850 points

    Hi Ramish,

    Thanks for your post, I can help you.

    The limiting factor of this TIPD107 design is the INA326. The INA326 has a bandwidth of 1kHz at unity gain. In a gain of 10V/V, your input signal frequency maximum limit is 100hz, as described in the design document. If you want to increase the input signal frequency range, I would recommend using a higher speed instrumentation amplifier (and possibly operational amplifier). 

    Before selecting an instrumentation amplifier / operational amplifier, please help clarify the following:

    • What are your power supplies?
    • What is the input signal? You mentioned 1V, is this sinusoidal? Is there a DC offset?
    • What is the expected output?

    We want to make sure our system requirements are met without violating any input or output conditions of the INA or OPA.

  • 0 in reply to Tamara M Alani
    Prodigy 10 points

    Actually, unity gain is fine since I only require a conversion from voltage to current. Would then the current amplifier be okay? 

    Also, the input signal can vary from a few mV up to 1 or 2V. The signal is not sinosuidal but more like a constant burst of voltage (5 us) which repeats every 3 ms. The expected output like I said is current (proportional to the input voltage) which can be read-out using an electrometer. The range of the electrometer is 1nA to 100 uA. 

    Thank you so much for your help!

  • 0 in reply to Ramish Ashraf
    TI__Genius 10850 points

    Hi Ramish,

    Thanks for the additional information. A 5µs burst would require a bandwidth above ~200kHz. The settling time of the INA326, in this case, would be the limiting factor. Please see this snippet from the datasheet:

     

    It may work, but it depends on what precision you need to settle to.