Hello ARoxas

Thank you for your reply. I uploaded the screenshot with higher resolution, sorry for that.

I took the headroom as the input voltage where the difference between input and output starts to increase. This is at approximately V+ - 3.5V.

I then…

The OP270 is a very ooooooold part;  not recommended for new design.

I would look at using the AD8672.

There is no current limit for the OP270, so it's a function of the output transistors.

I would use 30-40 mA for calculations.

Harry

Hi

Has this issue been resolved? In ADISimPE, the noise is still wrong (not matching datasheet) for AD8676.

In LTSpice I used AD8675 for simulation because there is no model for AD8676 but the results do not match the datasheet as well.

- Input Voltage…

把OP270换了在试试吧，例如AD8672等。

There two AD8512 and one AD8672 in the circuit.  This image is the first amp after the demodulator.

I need to increase the noise below 100 Hz.

Thanks....Steve

Hi Ching,

You can actually use any op amps as a buffer but I would recommend AD8542, ADA4001-2, or AD8672 because these are low noise, low input bias current op amps that suit your application.

Also, since you need only two buffers (one for each AD9681…

Bryan,

I wish you would have gotten a name so I could track this down further.  Was it a local field office

or an office in Norwood?   Which department?  That is certainly unacceptable behavior.

I was the product line apps engineer for the ADA4627-1. 

Hi Miguel,

I can see the same problem in both transitions (0->1 and 1->0), event though it's more likely to see the error when I switch to freq1.

I'll check again the power supply and the grounding, but I must say the PCB follows the rules…

I have some questions:

Are you able to use a 3-wire connection to the mic, or does your design require a 2-wire? The WM-60A is now obsolete because of RoHS non-compliance, I believe that the WM-61A is the compliant replacement. I have not run into the…