I have this following circuit; I use an Arduino DUE to send a 12-bit DAC output and I want to feed this in an Op Ampschematic.

Every ground is tied to the same ground. The Op Amp is ADA4000-2 from Analog device.

The USB power is used and DUE (SAM3 series MCU) outputs DAC output to the Op Amp input. Osci

I created a DAC signal that goes up/down from 1.55V. As you see the yellow signal (channel 1), this 1.55V is like a DC-Offset. The blue signal (channel 2) is the Vout pin, the output of the Op Amp.

If you take a close look at the part where the values are lower than 1.55V from channel 1, I was expecting the same decreasing pattern from channel 2. However, that part is constant to 4.1V and I think the output becomes saturated.

I cannot understand this reason. What seems to be the reason for this constant output? I wanted a unity gain, but I cannot find the reason for this. Appreciate your help.

  • 2
    \$\begingroup\$ electronics.stackexchange.com/questions/234575/… \$\endgroup\$
    – G36
    Commented Jan 17, 2019 at 19:18
  • 2
    \$\begingroup\$ Datasheet page 1 "±4 V to ±18 V operation": you're giving it a single +5V supply. "±" does not mean "approximately", it means "both positive & negative" -> minimum 8V supply. \$\endgroup\$
    – brhans
    Commented Jan 17, 2019 at 19:24
  • 2
    \$\begingroup\$ Then page 3: Input Charactersitics, Input Voltage Range: tells you that you can't apply an input any closer than 4V above the negative rail. Output Characteristics: tells you that it can't get any closer than about 1.5V to either supply rail. \$\endgroup\$
    – brhans
    Commented Jan 17, 2019 at 19:26


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