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I built a hobby mic op-amp circuit as described here:

mic op amp from https://lowvoltage.wordpress.com/2011/05/21/lm358-mic-amp/

It gave me a pretty ok result: enter image description here Now I replaced LM358 with LME49710. The circuit is the same, except from the wiring to the LME49710 pins (LM358 pin 1 is the output while it's pin 6 on LME49710, VCC also moved from pin 8 to 7, the rest are the same)

LME49710 is supposed to be a more high-end op-amp, so I expected some improvement. However... enter image description here

That doesn't look right and doesn't sound right. A lot of noise is added, and the audio is less amplified and hardly heard over the noise.

  • What are LME49710 characteristics that makes it less suitable for this circuit?
  • Is there a simple way to change the circuit and make it work better with LME49710?
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  • \$\begingroup\$ The LME49710 is a dual supply op amp. It is not a replacement for the single supply LM358. If you change you circuit to +/- 5V then it will bias correctly. \$\endgroup\$ Jun 23 '18 at 23:19
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I suspect it is honking somewhere ultrasonic!

The 49710 is an excellent part, but it is FAST (~50MHz GBP), where the '358 barely manages 1MHz GBP. Layout will be a LOT more important with the faster part, as will things like isolating load capacitance (100pF max by the datasheet) and capacitive loading of the inverting node.

I would instinctively be adding maybe 100R in series with C3 and something like 10pF or so across R5, but really the capsule self noise (And the noise contribution from the resistors is going to be large enough to swamp the use of an expensive opamp in that design.

If you placed a 50MHz GBP part on one of those white plug boards, you deserve whatever happens to you (Lots of strays in those things), get a bit of copper clad and dead bug the thing over a ground plane you will be MUCH more likely to get it to work.

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Here is an example: default opamp (UA741 clone) has UGBW moved up to 100MHz. A capacitive load of 100pF is added to output. And to cause lots of phaseshift, the Rout is increased from the default 100 ohms to 1,000 ohms.

Result: oscillation at 3MHz

enter image description here

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