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the circuit to set the reference dB = 0 point uses the AD637 integrated buffer and two external op-amps, one of which is obsolete.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 !