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I have 3pcs of AD633 chips, and the accuracy should be ±1% (typical), ±2% (max) according to datasheet.

I wired it like this:

enter image description here

I tried several input voltages, but it seems, that output is still way out of tolerance. For example:

IN1=7.008V
IN2=2.003V
OUT=1.4537V

Output should be precisely 1.4037V. But it's 3.5% out. All 3 my chips are out of tolerance (up to 5%).

I don't know if there is problem in my circuit? Or problem is that all of those chips are out of tolerance? (bought from China)

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    \$\begingroup\$ Tie the inputs together and tell us the output when input is 0 V, 1 V, 2 V, 3 V, etc. \$\endgroup\$ – Transistor Jul 28 '16 at 18:52
  • \$\begingroup\$ What are you using to measure these voltages? \$\endgroup\$ – brhans Jul 28 '16 at 18:58
  • \$\begingroup\$ You may have to separately account for DC offsets (what does it do when one input is exactly 0V) etc - when that's done, you may find it is within spec. Or not... \$\endgroup\$ – Brian Drummond Jul 28 '16 at 19:05
  • \$\begingroup\$ I started to do measurements suggested by transistor. Thanks to that, I noticed some shimmering on voltmeter's bargraph. I did not notice that before. So I found out that quality of used ±12V power source is the culprit. \$\endgroup\$ – Chupacabras Jul 28 '16 at 19:24
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I made very basic error. Problem was in quality of ±12V power source. After I added some capacitors, precision of those multipliers improved dramatically. enter image description here

Precision is within 1% now.

IN1=7.004V
IN2=2.0046V
OUT=1.4082V

So, now it is out by 0.3%. That is better :)

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  • \$\begingroup\$ Good work. Many are tempted to leave out the decoupling capacitors recommended by the datasheets. The question to ask is "what do these people know that the manufacturers don't"! You have now learned that lesson! Thanks for letting us know. \$\endgroup\$ – Transistor Jul 28 '16 at 19:37
  • \$\begingroup\$ I did not care about decoupling capacitors because datasheet says: "multiplier accuracy is essentially supply insensitive". \$\endgroup\$ – Chupacabras Jul 29 '16 at 5:43

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