It also play an important role in the transmission of electrical signals in nerve cells. RC circuit is common element in electronic devices. If a RC parallel circuit connected in series in the circuit, it can attenuate low-frequency signals, and if it connected in parallel in the circuit, it can attenuate high-frequency signals. RC circuits are widely used in analog circuits and pulse digital circuits. However, LC parallel circuits can resonate. In addition, simple RC parallel circuits cannot resonate, because resistor does not store energy. According to the arrangement of resistors and capacitors, it can be divided into a RC series circuit and a RC parallel circuit. Ⅰ RC Circuit Basics 1.1 What is RC Circuit?įor a RC circuit (resistor-capacitor circuit), the primary composes of a resistor and a capacitor. This produces a characteristic time dependence that turns out to be exponential. That is, a capacitor can store energy, and when a resistor placed in series with it will control the rate at which it charges or discharges. When connected to a DC voltage source, the capacitor charges exponentially in time. RC circuit (resistor–capacitor circuit), also called RC filter or RC network, has a resistor and a capacitor in series connection. This article mainly introduces the RC Circuit in series and parallel state. This is because capacitors are easier to manufacture with smaller size. In practice, capacitors (and RC circuits) are usually used instead of inductors to form filter circuits. They have some important properties for analog electronics, and can be used as passive filters. These components can be used to form 4 different circuits: RC circuit, RL circuit, LC circuit and RLC circuit. In the next article, we’ll see that the low-pass transfer function and the high-pass transfer function can be combined into a general first-order transfer function, and we’ll also briefly consider the first-order all-pass filter.As we all know, the most basic passive linear components are resistors (R), capacitors (C) and inductive components (L). We’ve examined the standard transfer function for a first-order high-pass filter, and we’ve seen how this transfer function leads to the characteristics of the high-pass magnitude and phase response. In other words, all low-frequency input signals will be shifted by 90°, and then the phase shift will begin to decrease as the input frequency approaches the pole frequency: The result of all this is that the high-pass filter phase response has an initial value of 90°. The phase shift reaches 90° at a frequency that is one decade above the zero frequency, but a high-pass filter has a zero at ω = 0 rad/s, and you can’t specify a frequency that is one decade above 0 rad/s-again, we’re dealing with a logarithmic scale here, which means that the horizontal axis will never reach 0 rad/s, nor will it ever reach a frequency that is one decade above 0 rad/s (such a frequency doesn’t really exist: 0 rad/s × 10 = 0 rad/s). $$\frac$$ High-Pass Filter Phase ResponseĪs mentioned above, a zero contributes 90° of phase shift to a system’s phase response, with 45° of phase shift at the zero frequency.
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