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Is AD637 dB calibration without buffer possible ?

Question asked by Spacerowa on Dec 20, 2016
Latest reply on Dec 21, 2016 by jstaley

In the AD637 data sheet Rev.L p18 fig.20 the circuit to set the reference dB = 0 point uses the AD637 integrated buffer and two external op-amps, one of which is obsolete. In any case this seems to be over-complex just to level shift a dc voltage.

However, in my AD637 project application which I am prototyping, I have already configured the buffer as a filter as mentioned elsewhere in the data sheet, so the buffer is committed. But I would also like to use the AD637 dB output, if for no other reason than to fill up the 2nd line on a two row lcd display module.

Can the circuit be simplified to allow calibration with no buffer ? What are the possibilities ?

Could it be just a pot between AD637 dB pin and ground with the connection to the board header 'dB output' taken from the slider ? If so what would be a suitable resistance ?

Or any other way which doesn't need the integrated buffer.

Incidentally, I'm not after the ultimate in accuracy, so we can forget about temperature compensation etc.

It would be a pity if it is an either/or situation; either filter or dB output but not both !