page_title: RL circuit
section_title: Parallel circuit
hierarchical_section_title: RL circuit / Parallel circuit
context_page_description: A resistor–inductor circuit, or RL filter or RL network, is an electric circuit composed of resistors and inductors driven by a voltage or current source. A first-order RL circuit is composed of one resistor and one inductor and is the simplest type of RL circuit.
  A first-order RL circuit is one of the simplest analogue infinite impulse response electronic filters. It consists of a resistor and an inductor, either in series driven by a voltage source or in parallel driven by a current source.
context_section_description: 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 Vₒᵤₜ is equal to the input voltage Vᵢₙ — as a result, this circuit does not act as a filter for a voltage input signal.
  With complex impedances:
  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) and is to be avoided.
caption: Parallel RL circuit