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This DAC has an output range of 1-3 volts. Here's the datasheet:

Datasheet

I'm getting pulses with different amplitudes, frequencies, duty cycles and widths varying from 0.2 ms to 2 s from the DAC. I want an output range of 0-4 volts instead (Vcc=5v). I tried a high-pass RC filter, and then amplified it with an op-amp, but the output doesn't look like a pulse anymore. Also, I tried the circuit suggested in the datasheet (page 8) with no luck. I'm not sure what values I should assign to this circuit, since I don't understand how it functions. How should I go about this?

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  • \$\begingroup\$ The circuit on page 9 is a band pass filter. \$\endgroup\$ – JRE Nov 12 '18 at 20:59
  • \$\begingroup\$ @JRE So, It wouldn't work for me, since I'm sending pulses. Am I right? \$\endgroup\$ – Mah Nov 12 '18 at 21:05
  • \$\begingroup\$ JRE: exactly, the first part and last part (passive C-R) are high-pass filter; but the active main part with the op amp is a low-pass filter 2nd order. See (sorry German): electronics-tutorials.ws/de/filtern/filter-zweiter-ordnung.html \$\endgroup\$ – Tom Kuschel Nov 12 '18 at 21:06
  • \$\begingroup\$ With slow transitions, you could directly connect an adder op amp like electronics-tutorial.net/analog-integrated-circuits/… \$\endgroup\$ – Tom Kuschel Nov 12 '18 at 21:13
  • \$\begingroup\$ You'll probably need to use an opamp to subtract the offset, and amplify the signal \$\endgroup\$ – JRE Nov 12 '18 at 21:14
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If you want pulses to stay looking like pulses, you need to avoid any circuitry that has any frequency response at all, but this DAC is clearly intended for audio use, where the output would be AC coupled to the next stage by a capacitor, but that's not possible if you want a near-DC response. If the output at a '0' input is predictable at 2V, to get from a 1-3V output to your desired 0-4V output you need to to subtract 1V and multiply by 2. Fortunately that's easy to do with a single op-amp.

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V2 is a reference voltage, you can do that with a divider of reasonably low impedance, or a reference voltage source. If you have a spare op-amp, using that as a buffer for the reference will stabilize things. V1 is the input from your DAC.

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