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

• Integrated circuits are cheaper to manufacture due to less material and lower assembly costs.
• They are more versatile and can include multiple functions in a single package.

A differential amplifier amplifies the voltage difference between its two input terminals. It has higher resistance on the input side, allowing it to reject noise and common-mode signals effectively, thus providing a cleaner output.

Negative feedback is typically used in amplifier circuits to stabilize gain and improve linearity.

Oscillator circuits often utilize positive feedback to generate sustained oscillations.

Positive feedback reinforces the input signal, leading to increased gain, while negative feedback reduces the gain and stabilizes the output, improving linearity and bandwidth.

The output voltage can be calculated using the formula: $V_{out} = V_{in} \left(\frac{R_f}{R_{in}}\right)$ Substituting the values: $V_{out} = 0.7 V \left(\frac{170 kΩ}{10 kΩ}\right) = 12.6 V$

The voltage gain of the amplifier is given by: $A_v = \frac{V_{out}}{V_{in}}$ Where: $A_v = \frac{12.6 V}{0.7 V} = 18$

One application of a monostable multivibrator is in timing applications, such as generating precise time delays.

The main difference is that a monostable multivibrator has one stable state and produces a single output pulse in response to a trigger, while a bi-stable multivibrator has two stable states and can maintain its output state until triggered to change.

The output waveform for the integrator op-amp will have a ramp shape, indicating the integration of the input signal over time.

The output will switch between high and low, forming a square wave as the input crosses the reference voltage.

The output will toggle with hysteresis, producing a square wave form from the triangular input signal.

The output will be a continuous waveform, indicating the summation of the input signals, inverted in phase.

Using the formula for an inverting amplifier: $V_{out} = -\left(\frac{R_f}{R_{in}}\right) V_{in}$ the output voltage calculation will yield: $V_{out} = -\left(\frac{200 kΩ}{20 kΩ}\right) \times 5 V = -50 V$

The gain is computed as: $A_v = -\left(\frac{R_f}{R_{in}}\right) = -10$

A Schmidt trigger is commonly used for shaping noisy signals into clean digital signals.

The resonant frequency is given by: $f = \frac{1}{2\pi\sqrt{LC}}$ For the given values: $L = 27 mH, C = 47 µF$, yields: $f = \frac{1}{2\pi\sqrt{27 \times 10^{-3} \times 47 \times 10^{-6}}} = 141.28 Hz$

The frequency is given by: $f = \frac{1}{2\pi RC}$ For the values: $R = 20 kΩ, C = 45 pF$: yields: $f = \frac{1}{2\pi (20 \times 10^{3})(45 \times 10^{-12})} = 57.76 kHz$