Your first circuit: an RC low-pass filter
Draw a complete circuit, set component values and run your first simulation.
We will build the classic RC low-pass filter: a voltage source, a resistor in series, and a capacitor to ground. The output is taken across the capacitor.
- Press R, click to drop a resistor, then right-click and press Esc to stop placing more. Press C and place a capacitor below and to the right.
- Press Ctrl+R before clicking to rotate a part. Make the capacitor vertical.
- Open the Component dialog (AND-gate icon), choose voltage, and place a voltage source on the left. Place ground (G) under the source and under the capacitor.
- Press F3 and click from pin to pin to draw wires. Pins connect only when a wire ends on the pin.
- Right-click the resistor, set Resistance to 1k. Right-click the capacitor, set Capacitance to 1u. Right-click the source, choose Advanced, pick PULSE and set Vinitial 0, Von 5, Tdelay 0, Trise 1n, Tfall 1n, Ton 5m, Tperiod 10m.
- Press F4 and label the capacitor node OUT.
- Press S and type .tran 20m. Click Run, then click the OUT node to plot its voltage.
You should see the output charging towards 5 V and discharging each half cycle. It does not jump instantly because the capacitor must charge through the resistor.
LTspice understands engineering suffixes: k, Meg, m (milli), u (micro), n, p. Careful: M means milli in SPICE, so use Meg for mega.