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Zorluk: OrtaCapacitors

In a multi-stage audio amplifier circuit, a capacitor is placed in series between the output of one transistor stage and the input of the next stage. What is the primary purpose of this coupling capacitor?

  1. A
    To store energy within a magnetic field to oppose sudden changes in circuit current
  2. B
    To convert the direct current power supply voltage into an alternating current audio signal
  3. To pass the alternating current audio signal while blocking the direct current bias voltageCevap
  4. D
    To conduct direct current continuously while insulating against alternating signal frequencies

Cevap

To pass the alternating current audio signal while blocking the direct current bias voltage
In multi-stage amplifiers, each transistor stage requires specific direct current (DC) biasing voltages to operate in its linear region. A coupling capacitor placed in series between stages acts as an open circuit to steady DC (XC=∞X_C = \infty at 0 Hz0\text{ Hz}), preventing the DC bias of one stage from disturbing the next, while exhibiting low capacitive reactance to alternating current (AC) audio signals, allowing the desired signal to transfer unimpeded.

Adım Adım Çözüm

1
Analyze the capacitive reactance formula in relation to frequency
XC=12πfCX_C = \frac{1}{2\pi f C}, meaning capacitive reactance is inversely proportional to frequency.
Determining how the component reacts to different signal types establishes its filtering and coupling characteristics.
2
Evaluate the behavior of the capacitor at zero frequency (direct current)
For DC (f=0 Hzf = 0\text{ Hz}), reactance XC→∞X_C \to \infty, effectively acting as an open circuit that blocks DC voltage.
Amplifier stages require separate DC operating bias voltages that must not interfere with adjacent stages.
3
Evaluate the behavior of the capacitor for audio frequencies (alternating current)
For AC (f>0 Hzf > 0\text{ Hz}), XCX_C drops to a low value, allowing the alternating signal voltage to pass freely to the next stage.
Coupling requires the time-varying signal information to transfer smoothly across the circuit without attenuation.

Anahtar Kavram

DC Blocking and AC Coupling Behavior of Capacitors
Tahmini Süre:1m 0s
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Capacitors

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