xCircuit

xCircuit is a electronic circuit simulator, it is compatible with spice simulator. I can simulate electronic circuit, including common analog elements, such as: resistor, capacitor, inductor, bjt, mosfet, diode, transformer, current/voltage source, and digital elements, such as: not, buf, and, nand, or, nor, xor, dff, dlatch.
xCircuit have 3 analysis mode: DC sweep, Transient, AC sweep. All can generate its waveforms.
After simulation, can get waveform of node voltage, voltage source current, you can play with waveform to get understanding of the circuit.