I want to do dc simulation of differential amplifier circuit, and this is my .cir file looks like:

enter image description here

When i run simulation, ngspice give me an erorr:

Supplies reduced to 0.1000% Warning: singular matrix: check nodes vin1 and vin1

Supplies reduced to 0.0000% Warning: singular matrix: check nodes vin1 and vin1

Warning: source stepping failed doAnalyses: iteration limit reached

run simulation(s) aborted

  • 1
    \$\begingroup\$ It would help others help you if you provided a text version of your image, as well as (if possible) a separate (intended) schematic which you believe mirrors your spice deck. I'm not inclined to sit down and read each and every drain, gain, source, and body connection you show in order to map out what you intended. A schematic makes it a lot easier to compare the text to what is intended, as well as judge same. \$\endgroup\$ – jonk Nov 24 '18 at 21:56
  • \$\begingroup\$ @jonk I work this on linux mint in terminal using vim editor to make that circuit description file, so i don't have schematic of that circuit. This is differential amplifier with active load(that 3 pmos transistors) and current mirror for polarization( nmos transistor M6 and M7). V4 is voltage on inputs (Vin1 and Vin2) of diff pair. \$\endgroup\$ – nemanja Nov 24 '18 at 22:35
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    \$\begingroup\$ I can't work with an image. Can't copy the text and it is too much trouble to attempt to replicate your results if I have to type it all in by hand. I understand what you are trying to achieve here. Whatever is the problem is likely some minor "typo" of sorts. Or a minor misunderstanding. But I've no energy to type all that in to find out. \$\endgroup\$ – jonk Nov 24 '18 at 22:39
  • \$\begingroup\$ Hint: What is setting the common mode input voltage? \$\endgroup\$ – The Photon Nov 24 '18 at 22:42

Your input voltage source (V4) is floating.

There is no path to provide it a reference to the ground node That makes the problem singular.


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