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A resistor–capacitor circuit (RC circuit), or RC filter or RC network, is an electric circuit composed of resistors and capacitors. It may be driven by a voltage or current source and these will produce different responses. A first order RC circuit is composed of one resistor and one capacitor and is the simplest type of RC circuit.
The RC time constant, denoted τ (lowercase tau), the time constant (in seconds) of a resistor–capacitor circuit (RC circuit), is equal to the product of the circuit resistance (in ohms) and the circuit capacitance (in farads):
Another common design is the "Twin-T" oscillator as it uses two "T" RC circuits operated in parallel. One circuit is an R-C-R "T" which acts as a low-pass filter. The second circuit is a C-R-C "T" which operates as a high-pass filter. Together, these circuits form a bridge which is tuned at the desired frequency of oscillation.
This circuit does not have a resistor like the above, but all tuned circuits have some resistance, causing them to function as an RLC circuit. An RLC circuit is an electrical circuit consisting of a resistor (R), an inductor (L), and a capacitor (C), connected in series or in parallel. The name of the circuit is derived from the letters that ...
A simple PoR uses the charging of a capacitor, in series with a resistor, to measure a time period during which the rest of the circuit is held in a reset state. A Schmitt trigger may be used to deassert the reset signal cleanly, once the rising voltage of the RC network passes the threshold voltage of the Schmitt trigger. The resistor and ...
The product τ (tau) = RC is called the time constant of the circuit. The ratio then depends on frequency, in this case decreasing as frequency increases. This circuit is, in fact, a basic (first-order) low-pass filter. The ratio contains an imaginary number, and actually contains both the amplitude and phase shift information of the filter.
Similarly, in an RC circuit composed of a single resistor and capacitor, the time constant (in seconds) is: = where R is the resistance (in ohms ) and C is the capacitance (in farads ). Electrical circuits are often more complex than these examples, and may exhibit multiple time constants (See Step response and Pole splitting for some examples.)
English: Phasor diagram for a double passive RC circuit with voltage gain. Date: 19th March 2011: Source: Self created using Inkscape: Author: Spinning Spark: Licensing.