How can I create a Programmable Gain Amplifier (PGA) using an OP Amp and DAC output from a PIC® MCU?

You can create a Programmable Gain Amplifier (PGA) using an OP Amp and DAC output from a PIC® MCU by placing the DAC in the feedback loop (Ri) of the inverting amplifier. The DAC will behave as a programmable resistor as it has a resistor network to change the voltage.

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The key is to NOT connect the VREF to ground or negative potential as this will create problems.

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