LMH6629: and LMH6629SDEVAL, creating a multistage trans-impedance amplifier

Part Number: LMH6629

I have the two components mentioned above, and was curious to know if I could use the LMH6629, in the first stage, as a trans-impedance amplifier, which will take input current from a PMT, or an APD, (which will have an intrinsic capacitance of roughly 8 to 20 pF. If I can use the LMH6629 to do that, I would then use the LMH6629SDEVAL board as a voltage multiplier as to amplify the output of the trans-impedance amplifier.

As a side note, the highest frequency this system will work with will be roughly 400 MHz.

Thank you for taking the time to read this!
 -  Dillon

1 Reply

  • Hi Dillon,

    400 MHz will be challenging for the LMH6629, but it should be possible to get close to that value while keeping the amplifier stable. The most important piece of information will be to narrow down the input capacitance value in order to make an accurate prediction of the circuit. Using a rough estimate of 15 pF for the input capacitance, the LMH6629 should be able to achieve around 375MHz of bandwidth at 400 kOhms of gain. This is assuming the application can handle some peaking in the response as well. It may be possible to hit 400 MHz, but the phase margin will likely be lower than recommended.


    Jacob Freet 
    High Speed Amplifiers