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AD605&AD8332 overshoot

Hi.Our team is developing new products on ultrasonic testing. We chose AD605 as the receiver VGA chip. However, we met a problem as the picture shows: Ultrasonic pulse would make the receiver overshoot although we have designer protection circuit before AD605. To deal with this problem, we found to solutions:1. disconnect the pulser, the protection circuit, let the waveform generator connect with AD605 directly, the waveform generator output square waveform smaller than the AD605 input range, as we increase gain, the overshoot come; 2. we bought ad8332 evk board as we thought it was the slew rate that AD605 Smaller than AD8332. Test like above description, finally, we found the overshoot just like the AD605 shows.

Could you please help us finding out why this happened and how to solve this problem.Thank you so much.

attachments.zip
  • Thanks for attaching the scope shots and diode circuit but one can't really tell much about looking at just the results. Pease send relevant schematic, input signal, etc. Also please include your expectations, i.e., what is your requirement for the circuit and what do you expect to see.

    Thanks,

    js

  • Hi jstaley,

    Thanks for your reply.The receiver schematic is simple: the diode protection circuit followed with AD8332 EVK board. Input signal is ultrasonic pulser waveform(In this experiment, we adjust PULSER voltage as 12Vpp square wave).

    Question is how I solve the big 'dead zone' problem of the amplifier because of the pluser and low slew rate of amplifier.

    A new picture attaching as follows. When i connect the Pulser with a 5MHz probe( working on pulse-echo mode), and put the probe on a steel block(time of flight is 16.7us),we found the echo signal was modulated because of amplifier distortion.

    So, could you please help us solving the amplifier distortion problem.

    Thanks.

  • Hello,

    I really need a schematic to offer any comment. I'm sure it is a simple schematic, but this is how we can communicate with accuracy. If it is confidential, then give a copy of the relevant parts to Eva Wang and she can send it to me only, via internal email.

    Best regards,

    js