Analog to Digital Converter

This looks like another example of someone asking for help with their homework assignment.

Hi, Peter. Actually, you're supposed to put a dab of quicksilver in the loaf before you set it afloat. It stops in the newsgroup right over the answer to the homework question. All ah see heer is a plain loaf. ;-)

Not that you really need this, but you might want to look at Analog Devices Appnote AN-289. No link -- as a bonus, you'll have to look it up yourself.

If it "seems that at the basic level its nothing more that a pulse oscillator circuit followed by a comparator", you've got a bit of a haul.

Good luck Chris

Successive approximation types are built around a D/A converter and comparator. You compare the input signal to the output of the D/A. Toggle the MSB of the D/A and if the D/A output is now too big (comparator switches) you turn that bit back off. Continue for all bits.

You can build a dead-simple D/A for this from a simple R-2R resistor ladder, driven by any decent CMOS digital output. A buffered printer port on an old PC works fine. Full discussion of this, and software to run it, at

Best regards,

Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis

Well, you have to give him a point for disguising it well^H^H^H^Hbetter than most. ;-)

Cheers! Rich

Or maybe that should be 9X 74HC148 ;-)

Oh, wait! That's a flash converter - the teacher wants an(a) SAR. >:->

Cheers! Rich