7.1 Explain what an operational amplifier (op amp) is - NSC Electrical Technology Electronics - Question 7 - 2017 - Paper 1

1. Compactness: Integrated circuits can incorporate many components into a single chip, minimizing space and reducing overall size in electronic circuits.
2. Cost-Effectiveness: They are generally cheaper to manufacture due to reduced parts and labor, lowering production costs for electronic devices.

A differential amplifier compares two input voltages and outputs a voltage that is proportional to the difference between these two inputs. It amplifies this difference while rejecting any voltage common to both inputs, known as common-mode voltage, which enhances signal integrity in applications like audio and sensor signal processing.

Negative feedback is commonly found in amplifier circuits, as it stabilizes gain and reduces distortion.

Positive feedback is typically used in oscillator circuits to maintain oscillation and generate sustained waveforms.

Positive feedback enhances and increases input signal deviations, potentially leading to instability or oscillation. In contrast, negative feedback reduces output fluctuations by feeding a portion back to the input with an opposite phase, improving stability and bandwidth.

Using the formula for an inverting amplifier:
V_{out} = - rac{R_f}{R_{in}} imes V_{in}
Here, (R_f = 170 k\Omega) and (R_{in} = 10 k\Omega):
$V_{out} = - \frac{170000}{10000} \times 0.7 = - 11.9 V$

The voltage gain (A) is calculated as follows:
$A_{v} = - \frac{R_f}{R_{in}} = - \frac{170 k\Omega}{10 k\Omega} = -17$

A common application of a monostable multivibrator is in pulse generation, such as creating a time delay for signal processing or as a debounce circuit in switch controls.

The main difference is that a monostable multivibrator has one stable state and changes its state upon triggering, while a bi-stable multivibrator has two stable states and switches between them based on triggering events.

The input waveform consists of a step function, and the output waveform will resemble a ramp function, indicating that the integrator creates a continuous voltage ramp over time.

The input waveform will appear as a triangular wave, while the output will produce a square wave, showing the switching behavior of the comparator based on input threshold levels.

The input will show a sinusoidal waveform, and the output will be a square wave triggered at defined upper and lower threshold values, demonstrating hysteresis.

The input waveforms will consist of multiple sine waves that interact, and the output should reflect the summation of these inputs, likely displaying a combined waveform characteristic of an inverting summing amplifier.

The output voltage can be calculated using the inverting amplifier formula:
$V_{out} = - \frac{R_f}{R_{in}} \times V_{in}$
Substituting in values:
$V_{out} = -\frac{200 k\Omega}{20 k\Omega} \times 5 V = -50 V$

The gain is calculated as follows:
$A_{v} = - \frac{R_f}{R_{in}} = - \frac{200 k\Omega}{20 k\Omega} = -10$

A Schmidt trigger is often used to convert analog signals to digital signals, providing clean signal transitions and eliminating noise.

The resonant frequency is calculated using the formula:
$f = \frac{1}{2\pi\sqrt{LC}}$
Substituting values:
$L = 27 mH, C = 47 \mu F$
$f = \frac{1}{2\pi\sqrt{(27\times10^{-3})(47\times10^{-6})}} \approx 141.28 Hz$

The frequency can be calculated using the formula:
$f = \frac{1}{2\pi RC}$
Here, (R = 20 k\Omega, C = 45 pF):
$f = \frac{1}{2\pi(20 \times 10^3)(45 \times 10^{-12})} \approx 57.76 kHz$