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OPA1652: Replacing OPA2134 with OPA1652

Part Number: OPA1652
Other Parts Discussed in Thread: OPA2134, TINA-TI


Could you please give us your advice whether we can replace OPA2134 with OPA1652 in the following schematic or not ?

Best regards,

  • Kato,

    OPA2134 and OPA1652 are both SoundPlus type of high performance audio JFET amplifiers with very similar datasheet specifications and thus you should be able to swap them in SO-8 package (OPA1652 is not available in PDIP).  The only concern I would have is in the case you attempt to drive a large capacitive load - a capacitive load connected between the output and ground (ac coupling C109 and C110 caps shown in your schematic should not be a problem).  

    While OPA2134 can easily drive 1nF in G=-1, OPA1652 cannot drive more than 230pF - see Small-Signal Overshoot vs Capacitive Load graphs below:

  • Hi Marek-san,

    Thank you for your comment.

    I simulated OPA1652 to verify the stability by using TINA-TI as below, so I believe that that is no issue but would like you to confirm just in case.

    Best regards,

  • Hello Sadanori,

    The simulation you provide is does not necessarily confirm stability. You need to disturb the system with a small-signal step signal and observe the output or break open the feedback loop and determine the phase margin. I have done the latter.

    I broke open the feedback loops of each amplifier at the inverting inputs with a 1T Henry inductor and injected my signal source there with 1 TF capacitor. You can probe for loop gain (AolB) and loaded open-loop gain (Aol). You can also calculate in post-processing 1/B with Aol/AolB to determine rate-of-closure.

    Here are the circuits and AC characteristic plots. Both stages had phase margins of ~75degress which is definitely stable. This analysis would need to be repeated if there are any capacitors at the final loads. Note I included the effects of OPA1652 input capacticance with Cin = Ccm + Cdiff.









    Peter Iliya

    Precision Amplifiers Applications

  • Hi Peter-san,

    Thank you for your special support.
    I understood that the OPA1652 simulation you would provide to me is stable with the phase margin.

    Best regards,