Define the term stability with reference to the Q-point of amplifiers - NSC Electrical Technology Electronics - Question 6 - 2023 - Paper 1

The class of amplification represented in FIGURE 2.2 is Class A amplification.

The output waveform should be representative of a Class A amplifier, characterized by a linear output that closely follows the input signal.

To determine the voltage drop across Rc, use the equation: $V_R = I_C imes R_C$ where $I_C$ is the collector current.

Using the characteristic curve, identify the operating point (Q-point) and apply the formula for the load resistor: $R_L = \frac{V_{CC}}{I_C}$ where $V_{CC}$ is the supply voltage.

The gradient of the load line increases as the load resistance decreases, which allows more current to flow for a constant supply voltage, thus illustrating greater power handling capacity.

Capacitors C1 and C2 primarily serve to couple AC signals while blocking DC components.

The circuit is classified as an audio amplifier because its input and output frequencies align with the audio frequency range, facilitating sound signal amplification in microphones and earphones.

Capacitor C3 provides a low-resistance path for AC signals, allowing audio frequencies to pass while filtering DC biases.

Capacitors C4 and C5 are used for coupling and decoupling within the amplifier stages, ensuring stable operation and preventing unwanted oscillations between stages.

One advantage is impedance matching, which enhances power transfer between stages, improving overall efficiency.

T1 is utilized to couple the output of the first stage to the input of the second stage, ensuring that the amplified signal is transmitted without degradation.

A disadvantage of the amplifier in FIGURE 6.6 is its potential for distortion when subjected to high input signals.

Transistor Q2 acts as a switching element within the circuit, controlling the output stage in response to the input signal.

The output waveform should depict the switching action of Q2, which corresponds to the input signal's variations.

Radio frequency amplifiers are designed to amplify high-frequency signals, enhancing their strength for further processing.

The term for unwanted frequencies in radio frequency amplifiers is 'noise'.

LC-tuned circuits provide selectivity at specific frequencies, allowing for better reception and amplification of desired signals while rejecting unwanted ones.

Electrolytic capacitors are employed in LC-tuned circuits due to their higher capacitance values, which are essential for achieving desired filter characteristics.

One application of the Hartley oscillator is in radio frequency signal generation.

Transistor Q4 is utilized to replace the energy that is lost during each cycle, ensuring continuous oscillation generation.

The output waveform should show the oscillatory output produced by the Hartley oscillator, clearly displaying its frequency characteristics.

The function of resistor Rc is to control the collector current in order to protect the transistor from excessive load.

Using the formula for the oscillation frequency: $f_0 = \frac{1}{2\pi \sqrt{6RC}}$ and substituting $R = 10,000 \Omega$ and $f_0 = 56.36 Hz$, yield a capacitance of approximately $C = 100 nF$.

The oscillation frequency will decrease as the value of the capacitor increases because the oscillation frequency is inversely related to capacitance in the phase-shift oscillator configuration.