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OPA4350: vs OPA4340

Part Number: OPA4350
Other Parts Discussed in Thread: ADS1204, OPA4192, OPA4340, OPA4197, TINA-TI, OPA336

We are trying to determine if the OPA4340 would work as well as the OPA4350 in the circuit on page 14 of the ADS1204.  Our input signals are sinewaves with a frequency less than 5KHz, as we are using chip in conjunction with the AMC1210IRHA for resolver sin and cos signals.  We are using 33 Ohm and 0.01uF, instead of the 27 Ohm and 0.1uF shown.  Are there other Op Amps that would work as well?  We are wondering about other options (such as OPA4192 or OPA4197), as all these Op Amps can have very long lead times.

  • HI Conrad,

    The OPA4340 with the 33-ohm and 10nF will work well. (EDIT: Updated simulations with 33-ohm and 10nF below)

    Below is the closed loop DC and AC TINA-TI frequency sweep, as well as the open-loop AC stability analysis.

    OPA4340 Closed Loop AC and DC sweep:

    OPA4340 Closed-Loop TINA-TI File: Stability2_OPA4340.TSC

    OPA4340 Open-Loop AC Stability Analysis:

    OPA4340 Stability Analysis TINA-TI File: Closed_loop2_OPA4340.TSC

    However, the OPA336 2.5V buffer shown on page 14 driving the 100nF capacitor directly could be un-stable.  I recommend you change the OPA336 circuit to use a dual-feedback configuration to ensure stability.  One possible circuit is below:

    OPA336 Open-Loop AC Stability Analysis:

    OPA336 Stability Analysis TINA-TI File: 


    Thank you and Regards,



  • HI Conrad,

    Updated the simulations above using the OPA4340 with 33 Ohm and 0.01uF, as you requested.  Let me know if you have questions.

    Kind Regards,