for_help_in_forum.qsch (9.0 KB)
ADA4841.qsym (696 Bytes)
ada4841.txt (7.3 KB)
This circuit complains about a singular matrix when I connect PD\ to +5V on Qspice but simulates when PD\ is connected to ground. I recreated the circuit in LTspice and it worked fine when PD\ was connected to +5V.
I tried setting .options gmin 1e-12 and also tried connecting PD\ +5V through a 100Meg resistor, but neither of these things corrected the issue on Qspice.
I appreciate the help!
If you put this netlist into LTspice, with PD connected to +5V, you can observe that to solve the operating point, Direct Newton iteration failed and requires Gmin stepping. In total, LTspice needs 16 rounds of Gmin stepping to find the operating point. In LTspice, the default .option gminsteps=25 represents the maximum allowed iterations in Gmin stepping, set to 25 times.
For Qspice, the default .option gminsteps is 10. Therefore, by including .option gminsteps=25, this circuit will be able to calculate its DC operating point.
