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,
Kato
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.
Best,
Peter Iliya
Precision Amplifiers Applications
