# Please explain why datasheet says to connect the feedback resistors in a particular way

The datasheet for the AD667 DAC shows how to connect the output to internal feedback resistors in different ways, in order to get different output voltage ranges.

• For output range of 0 to +5 V, it says to connect the output to pin 2, a 5k feedback resistor.
• For output range of 0 to +10 V, it says to connect the output to both pins 1 and 2.

Pin 1 is also a 5k feedback resistor, which is in series with the pin 2 feedback resistor. So it seems that the feedback current would all go through pin 2, because the pin 1 feedback resistor is in parallel with a short.

It would make more sense to me if it said to connect pin 9 to ONLY pin 1 to get an output range of 0 to +10 V, that way the feedback resistance is 10k, twice as much as 5k, twice as much gain, so 10 V range instead of 5 V range.

Can anyone explain why they connect pin 9 to both pins 1 and 2?

• Connecting just pin 1 to pin 9 gives you a 20V range, not 10V. You should include more of that table instead of cropping off the fourth column. Commented Jun 12 at 0:17