Several base current values on the same graph

Question

I need to have several base current values on the same graph with the output characteristics of the NPN transistor, which I set using Rb.

How can I make them on the same graph?

Answer 1

Use the "STEP PARAM" command:

.step param RX list A B C D E F G

If you change R6's resistance value (1000) to something like {RX} (just a name and can be anything) and add the LTSpice directive above to your simulation, the simulation will run each time with the next (A, B, C ...) RX value applied to R6. I put 7 values as example but can be 2, 3, or 10.

For example, if you want to run the simulation for R6 = 1k, 1k2, 1k3 and 1k5, add the following command:

.step param RX list 1000 1200 1300 1500

This will run the simulation for each value and plot the curves on the same waveform. For details, see here and here.

Answer 2

If you would like to have in your diagram equally spaced base currents I recommend to use not a voltage source with a resistor at the base but instead a current source which can be stepped through different values (use param feature of the program).

Answer 3

In CircuitLab you can Run a DC Sweep with a Second Parameter

^{simulate this circuit – Schematic created using CircuitLab}

You can click on the simulate this circuit link above to enter the CircuitLab simulator.

Answer 4

You can .dc a current source into the base and plot the collector current: