I am attempting to convert the differential output of a DAC to a single-ended signal using the following circuit from a TI datasheet:
The signals going into this amplifier look like this:
And the output signal looks like this:
The Op-amp I am using is the LMC6484 (rail-to-rail) with V- to GND and V+ to +5V. My understanding is that the subtraction of signals results in a negative value for half of the waveform resulting in the clipping behaviour. What I am looking for is a way to bias the signal to avoid this clipping? I am trying to avoid having to add a negative voltage rail.
I am having a hard time figuring out how this is possible. Any suggestions?
Best Answer
Your feeding a diff signal with a + and - voltage swing, but your power supply is single-ended, with no negative rail, so the negative part of your signal is being cut off. For this to work you need an op-amp with +/- 5 volt power rails.
For single -ended power supply issues: Add a 10K ohm pot from +5 volts to ground. Remove the grounded end of R2 and connect it to the wiper of the pot. This will provide a positive offset and shift the signal up ward. If it clips on the + 5 volt rail then reduce the values of both R2's by 1/2.
Over time you can fine-trim R2 for maximum size without clipping.