KSKelvin. The high output level is formed by Darlington. That is, the output level is not equal to the supply voltage, unlike CMOS timers. I suggest a small upgrade of the model.
NE555_comp.qsch (13.7 KB)
NE555_comp.qsch (13.7 KB)
@bordodynov Is this the change you recommended in the model? Is there anything I may have missed? The model I developed is generally closer to a device in a textbook rather than being match to the datasheet, which is why there may be room for improvement.
B3 Out COM V=if(V(Q)>0.5,V(Vcc)-0.9,0) Rser=30
You recommend Rser=30 or =40? The netlist in .qsch is 30 but comment is 40.
I was looking for a compromise value and settled on 30 ohms. Have you noticed how your model does not correctly calculate the current of the load capacitor? The resistor improves the situation.
1 Like
My symbol library has been updated. Rout and headroom voltage are implemented as instance parameters, allowing users to adjust them based on the physical conditions. Additionally, a new symbol with an internal circuit drawing (555Timer-4.qsym) has been created, and the width of the box of -1/-2/-3 has been adjusted to better match with your 555 timer.
Also updated NE555 in qspice-alternative directory, which contains alternative symbols for the built-in NE555 in Qspice.
1 Like
Oh, thank you for your review and suggestions! Upon checking the datasheet, I realized that the headroom can be up to 1.7V. After comparing it with your symbol, I found that it better matches at a headroom of 1.2V. I also updated the output B-source with IC=0 to ensure it does not output voltage in the DC operation point calculation.
NE555_comp.qsch (9.5 KB)