AD8307 Response to Sin and Square Waves

During the engineering phase of a project, there most likely, or should be a time where a question will arise that will take you off in another direction. Latest examples of this are the characterizing of amplifier outputs at RF frequencies, AD8307 behavior with sin and square waves, and RF measurement techniques. All of which can involve a considerable amount of research time that adds to the project development phase. It's not necessarily a bad thing, and one of the things I like about the hobby.

Another thing that can happen is while doing this research, new projects come to mind as I contemplate new found knowledge.  The SNA project has brought in for consideration a VNA. Learning more about complex impedance's and how to measure them has now got me thinking about a project involving the AD8302 board I bought on spec a while ago.  Now that I have amplitude and phase I can do some interesting calculations.  Except now I have to learn how to do polar charts and of course the intricacies of the 8302. Again all fun.

I made some comparisons between two AD8307 chips.  One smd sourced from eBay and the other a dip package from Digikey.  The Digikey part was sourced about 5 years ago.  I ran the test using both Sin and Sq waves.

Interesting results. In that the the package type overall did not really differ and I'll come back to that. There is enough of a difference between the sin and sq wave that I think you would need to  consider the signal type when making measurements.  Especially at the lower frequencies.

The sq wave results are very linear and the sin wave not as good but still not bad at all.  Considering that the 8307 output is 25mv/db,  I'd say you definitely would need to be aware of what you are measuring when taking the readings.  Here are the numbers for the spread between the sin and sq waves:
 

71

62

51

40

29

17

5