Electronics | AQA A-Level Physics (7408)
Electronics
- 362 questions
- 18 subtopics
- Paper 3 Section B: one option of five
- Paper 3
Electronics is one of the five optional topics, sat on Paper 3.
It covers the semiconductor devices and sensors used to detect a signal, the operational amplifier circuits used to condition it, digital logic, and the systems used to transmit it.
Sample questions from Electronics
Answer each one closed book first, then open the answer.
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MOSFET (metal-oxide semiconducting field-effect transistor)
Define VGS for a MOSFET.
Show the answer
VGS is the voltage between the gate and source terminals. -
Photodiode
In photo-conductive mode, what bias condition is applied to the photodiode?
Show the answer
A reverse bias is applied. -
Difference between analogue and digital signals
What is sampling rate and what unit is it measured in?
Show the answer
The sampling rate is the number of samples taken per second, measured in hertz. -
The ideal operational amplifier
Explain why an ideal operational amplifier draws no current from the signal source connected to its inputs.
Show the answer
Because it has infinite input resistance, so no current flows into either input terminal. -
Non-inverting amplifier configuration
Under what resistor conditions does a non-inverting amplifier achieve its minimum gain of unity?
Show the answer
Unity gain occurs when Rꜰ = 0 or when R₁ is infinite. -
Real operational amplifiers
Why might a real op-amp produce a small output voltage even when both inputs are at exactly the same potential?
Show the answer
Because real op-amps have a non-zero input offset voltage arising from internal component mismatches. -
Sequential logic
What happens in a counter circuit each time a clock pulse is received?
Show the answer
The count advances by one state. -
Principles of communication systems
In the block diagram of a real-time communication system, what is the central stage that connects the transmitter to the receiver?
Show the answer
The transmission channel.
The 18 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| MOSFET (metal-oxide semiconducting field-effect transistor) | The gate, source and drain, the threshold voltage, and using a MOSFET as a switch. | 17 |
| Zener diode | The characteristic in forward and reverse bias, breakdown voltage, and voltage regulation. | 15 |
| Photodiode | Responsivity, photo-conductive mode, and detecting particles with a scintillator. | 27 |
| Hall effect sensor | How a Hall sensor detects a magnetic field, and its use in a tachometer. | 8 |
| Difference between analogue and digital signals | Bits and bytes, sampling rate, quantisation, and pulse code modulation. | 30 |
| LC resonance filters | The resonant frequency of a parallel LC circuit, bandwidth, and the Q factor. | 20 |
| The ideal operational amplifier | Infinite gain and input resistance, zero output resistance, and the two input terminals. | 14 |
| Inverting amplifier configuration | The gain formula, the virtual earth, and the phase inversion at the output. | 16 |
| Non-inverting amplifier configuration | The gain formula, why the minimum gain is one, and the phase relationship. | 12 |
| Summing amplifier configuration | The weighted sum of several inputs, and the difference amplifier that rejects a common signal. | 16 |
| Real operational amplifiers | Finite gain, the gain-bandwidth product, slew rate and offset voltage. | 28 |
| Combinational logic | The gates and their truth tables, and building larger functions from NAND or NOR. | 29 |
| Sequential logic | Flip-flops, the clock, binary and Johnson counters, and the reset and up/down inputs. | 22 |
| Astables | The RC time constant, mark-to-space ratio and duty cycle, and varying the running frequency. | 25 |
| Principles of communication systems | The block diagram of a real-time system, and the role of the transmitter and channel. | 17 |
| Transmission media | Metal wire, optic fibre and radio, and the trade-offs of bandwidth, attenuation and interference. | 24 |
| Time-division multiplexing | Interleaving sampled signals into frames, and keeping transmitter and receiver in step. | 12 |
| Amplitude (AM) and frequency modulation (FM) techniques | Modulating a carrier by amplitude or frequency, the bandwidth each needs, and reading the waveforms. | 30 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
AQA A-Level Physics Active Recall Guide
Every topic, not just this one. 3,682 questions with their answers.