AD8618 supply decoupling


I'm designing a PCB with four AD8618, single supply +3V and all channels as voltage followers (see attached figure, U3-U6). U1 is the voltage regulator in the circuit, and the output is decoupled with a 4.7uF tantalum cap (C2). Now my question is whether I actually need the decoupling caps on the op-amps (C5-C12). I'm using two decoupling caps per op-amp, one 0.1uF ceramic and one 10uF tantalum. The PCB traces between U1 and U4 (as well as U1 and U5) is approx. 4 cm. The traces between U1 and U3 (as well as U6) is approx. 10 cm.

If you please have some ideas on this I would be very grateful!

Thanks in advance,


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  • Elias,

      What does TRRS mean??

      What is your highest signal frequency?

      Depending on whether you need to go to DC or not and can AC couple, you could use op amps

    that have millivolts of offset, rather than <100 uV which drives up the price.

      Also, if your highest frequency is in the tens of kiloHertz range, you could use a lower gbw which

    will also reduce the possibility of oscillations.  Faster is not always better.

    Based on that, you could use what I call some "non-precision" op amps, such as the AD8592,

    AD8532, AD8602.  1k price less than $0.50 USD.

    Other possibilities would be AD8692, AD8646. AD8617, AD8604, etc.


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