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Presence of offset in the output

Ajit Singh1
Prodigy 100 points
Other Parts Discussed in Thread: OPA4350, TLE2426

Dear All,

   I have designed an ultrasonic receiver using opa4350 IC. One part of it is used to implement a band pass filter with Center Frequency of 25k. OPA4350 is a rail to rail IC. But output of my circuit is restricted to 400mv-4V range when I am using the supply voltage 0-5V. Can somebody point out the problem?

Ajit singh

25KOPA43501.TSC
  • 0
    TI__Guru* 93105 points

    Hi Ajit,

    I do not find an obvious issue with your OPA4350 filter/amplifier application circuit that would result in the output swing being restricted. Here are some questions that I have:

    • Do you have a load on the output of the amplifier section?
    • Have you observed the input signal, filter and amplifier output points with an oscilloscope as you increase the drive level?
    • When the output swing does become limited what do you see? Is it clipped, distorted, or is any oscillation present?
    • Did you obtain the OPA4350 device from the TI sample service, or a TI distributor?

    Something that I would recommend is including the recommended power supply bypass capacitor at the device supply pin and adding a capacitor at the TLE2426 rail splitter output. The supply line and non-inverting inputs of the two OPA4350 stages should be at the ac ground potential.

    Regards, Thomas

    PA - Linear Applications Engineering

     

  • 0 in reply to Thomas Kuehl
    Guru 21975 points

    Ajit,

    It appears that R4 presents a 100-ohm load to U1. Though the signal is small at this node the op amp may not behave as expected with this low-Z load due to its common-source output stage. These effects may not be accurately modeled in the macro model.

    Regards, Bruce.