I am trying to simulate a simple linear regulator using gschem and ngspice. However, my output voltage varies by over a volt as my input voltage goes from 10V to 20V. Can I reduce this swing in the output voltage by changing circuit parameters or is this a characteristic of linear regulators?
My circuit looks like this:
And the netlist that gets generated (witl the comments and models stripped out) is this:
V1 Vin 0 16.8 C2 0 Vout .1uF C1 2 0 1000uF D1 2 0 1N4004 R5 q1base 0 1k R4 q1base 3 5k R3 Vout 3 1k R1 q2base Vin 2k Q1 q2base q1base 2 2N4401 Q2 Vin q2base 1 2N4401 Q3 Vin 1 Vout TIP29 .end
When I perform a dc sweep on v1 by doing
dc v1 5 25 .1 my output is as follows: