Editing RL circuit (section)

==Parallel circuit==
[[image:RL Parallel Filter (with I Labels).svg|thumb|right|250px|[[series and parallel circuits#Parallel circuits|Parallel]] RL circuit]]

When both the resistor and the inductor are connected in parallel connection and supplied through a voltage source, this is known as a RL parallel circuit.<ref name=":0" /> The parallel RL circuit is generally of less interest than the series circuit unless fed by a current source. This is largely because the output voltage ({{math|''V''<sub>out</sub>}}) is equal to the input voltage ({{math|''V''<sub>in</sub>}}); as a result, this circuit does not act as a filter for a voltage input signal.

With complex impedances:
:<math>\begin{align}
 I_R &= \frac{V_\mathrm{in}}{R} \\
 I_L &= \frac{V_\mathrm{in}}{j\omega L} = -\frac{jV_\mathrm{in}}{\omega L}\,.
\end{align}</math>

This shows that the inductor lags the resistor (and source) current by 90°.

The parallel circuit is seen on the output of many amplifier circuits, and is used to isolate the amplifier from capacitive loading effects at high frequencies. Because of the phase shift introduced by capacitance, some amplifiers become unstable at very high frequencies, and tend to oscillate. This affects sound quality and component life, especially the transistors.