7.1 Name THREE applications of an operational amplifier (op amp) - NSC Electrical Technology Electronics - Question 7 - 2017 - Paper 1

An ideal operational amplifier possesses the following characteristics:

1. Infinite Input Impedance: No current is drawn from the input source.
2. Zero Output Impedance: Provides maximum power transfer to the load.
3. Infinite Open-Loop Gain: The gain of the circuit can be considered at its maximum.

The term 'open loop' in operational amplifiers refers to the configuration where the output is not fed back to any of the input terminals. This means that there is no feedback, and as a result, the gain of the circuit is at its maximum.

To illustrate an inverting voltage comparator, the schematic should depict the op-amp with the input signal on the inverting terminal, a reference voltage at the non-inverting terminal, and the output signal representing the comparison result.

Positive feedback occurs when a portion of the output signal is fed back to the input in the same phase, enhancing the total gain of the system. It can lead to instability but is beneficial in certain applications like oscillators.

The very high input impedance of an op amp minimizes the loading effect on preceding circuits. This means that there will be negligible current drawn from the preceding circuit, preserving the signal voltage.

Applications of RC phase shift include:

1. Audio Oscillators: Used for generating audio frequencies.
2. Phase Shift Oscillators: Employed in signal generation.
3. Filter Circuits: Used in shaping frequency response.

The waveforms should depict the same frequency with the output signal phase-shifted relative to the input if inverting or non-inverting as per the defined configuration.

The feedback resistor Rf feeds the output signal back to the inverting input, allowing control over the overall gain of the operational amplifier. It determines how much of the output is fed back, impacting the stability and performance of the circuit.

Decreasing the value of R in the feedback path will result in a decrease in the feedback voltage at the inverting input, which will increase the overall gain of the circuit, amplifying the output more significantly.

The resistor Rin controls the input impedance of the op-amp circuit. It can affect the input signal level and dynamically adjusts the gain and response of the operational amplifier.

The diagram should depict a Hartley oscillator using an inductor-capacitor (LC) circuit configuration, showcasing the arrangement of the inductors and capacitor used for oscillation generation.

If both input signals to a comparator are equal, the output will be zero. This is because a comparator only amplifies the difference between the two signals.

This change in amplitude during the amplification process is referred to as 'gain'. Gain quantifies how much the input signal is amplified to produce the output.

The natural oscillation frequency is defined as the frequency at which a system generates oscillations naturally without external forcing. Its graphical representation should illustrate three complete cycles of the waveform, showing the period and amplitude consistent with this frequency.

Feedback in operational amplifier circuits is applied to stabilize gain, improve bandwidth, and enhance linearity. It ensures that the output responds proportionally to the input signals, effectively linking different stages of complex circuits.

A non-inverting amplifier configuration maintains the phase of the input signal. An example application is in audio equipment, where it is used to amplify weak audio signals without inverting the waveform shape.