Hi,
Customer has the following schematic. Positive input is a 0-3.3v analog input. The negative input is a 0-3.3v pwm input. Both inputs need to be gained up to 0-5v at the output.
Simulation works great on an ideal op-amp but breaks when the actual LMC7101 is used. The analog input to gained output works great. However, the PWM only goes to 1V peak to peak. PWM is 10khz frequency 0-3.3v square wave.
The designer is primarily a digital designer so this is likely a cookbook problem. Does a 3.3v input on the DAC input for IN+ effectively make a 1.6V IN+ node with the 20K resistor to ground?
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I pulled up the following circuit that looks very similar - albeit with negative voltages rather than ground. It would imply they should ground IN+ rather than take it to 3.3v? Thoughts?