A "coupling capacitor" where the capacitor is used to bond a signal from one part of a circuit to another but without allowing any direct current to flow.
Use of coupling capacitor in analog circuits is to connect two circuits such that only the Alternating Current signal from the first circuit can pass through to the next while Direct Current is blocked. This technique helps to separate the DC bias settings of the two coupled circuits. Capacitive coupling is also known as AC Coupling and the capacitor used for the purpose is known as a Coupling or DC blocking capacitor.
Capacitive coupling has the disadvantage of degrading the low frequency performance of a system containing capacitively coupled units. Each coupling capacitor along with the input electrical impedance of the next stage forms a high-pass filter and each successive filter results in a cumulative filter with a -3dB frequency that may be higher than each individual filter.
So for sufficient low frequency response the capacitors used must have high capacitance ratings. They should be high adequate that the reactance of each is at most a tenth of the input impedance of each stage, at the lowest frequency of interest. This disadvantage of capacitively coupling DC biased, transistor amplifier circuits is largely minimized in directly coupled designs.
AC coupling is also broadly used in digital circuits to spread digital signal with a zero DC constituent, known as DC-balanced signals. DC-balanced waveforms are useful in communications systems, since they can be used over AC-coupled electrical connections to stay away from voltage imbalance problems and charge accumulation between connected systems or apparatus.
Mostly coupling capacitors are used in an audio system the signals must pass through with little or no distortion. This is achieved if the time constant (RC) is larger than the time period (T) of the lowest frequency audio signals required.
Use of coupling capacitor in analog circuits is to connect two circuits such that only the Alternating Current signal from the first circuit can pass through to the next while Direct Current is blocked. This technique helps to separate the DC bias settings of the two coupled circuits. Capacitive coupling is also known as AC Coupling and the capacitor used for the purpose is known as a Coupling or DC blocking capacitor.
Capacitive coupling has the disadvantage of degrading the low frequency performance of a system containing capacitively coupled units. Each coupling capacitor along with the input electrical impedance of the next stage forms a high-pass filter and each successive filter results in a cumulative filter with a -3dB frequency that may be higher than each individual filter.
So for sufficient low frequency response the capacitors used must have high capacitance ratings. They should be high adequate that the reactance of each is at most a tenth of the input impedance of each stage, at the lowest frequency of interest. This disadvantage of capacitively coupling DC biased, transistor amplifier circuits is largely minimized in directly coupled designs.
AC coupling is also broadly used in digital circuits to spread digital signal with a zero DC constituent, known as DC-balanced signals. DC-balanced waveforms are useful in communications systems, since they can be used over AC-coupled electrical connections to stay away from voltage imbalance problems and charge accumulation between connected systems or apparatus.
Mostly coupling capacitors are used in an audio system the signals must pass through with little or no distortion. This is achieved if the time constant (RC) is larger than the time period (T) of the lowest frequency audio signals required.
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