ElectronicsQ&A by dot point

Active filters: op-amp low-pass and high-pass filters, the cut-off frequency, pass-band gain, band-pass filters, and the advantages over passive filters.

Audio systems: the audio chain, voltage and power amplification, gain in decibels, amplifier classes (A, B and AB), crossover distortion, and bandwidth.

Comparators and Schmitt triggers: the open-loop comparator, the difference between a comparator and an amplifier, positive feedback, hysteresis, and switching thresholds.

Instrumentation systems: sensors and transducers, the Wheatstone bridge, the instrumentation (difference) amplifier, common-mode rejection, and signal conditioning.

Operational amplifiers: the ideal op-amp properties, the inverting, non-inverting, summing and difference amplifiers, the voltage follower, and the virtual earth.

AC signals and reactance: amplitude, peak-to-peak, period and frequency of a sinusoid, root-mean-square values, and the frequency-dependent reactance of capacitors and inductors.

Capacitors and inductors: capacitance and stored energy, the RC time constant and exponential charge and discharge, inductance and stored energy, and combining capacitors in series and parallel.

Circuit fundamentals: charge, current, voltage and resistance, Ohm's law, Kirchhoff's current and voltage laws, combining resistors in series and parallel, and electrical power.

Passive filters: RC low-pass and high-pass filters, the cut-off frequency, voltage gain in decibels, and reading a frequency-response (Bode) plot.

Potential dividers: the divider equation, loading effects, and sensing circuits using thermistors, light-dependent resistors and strain gauges to convert a physical quantity into a voltage.

Thevenin's theorem: replacing a linear network by an equivalent electromotive force and series resistance, finding the Thevenin voltage and resistance, and the maximum power transfer condition.

Timing circuits: the 555 timer in astable mode (frequency, period and duty cycle) and monostable mode (pulse duration), and oscillators for clock generation.

Number systems: binary, denary and hexadecimal conversion, binary addition, two's complement for signed numbers, and binary-coded decimal.

Combinational logic design: deriving a Boolean expression from a truth table (sum of products), minimising with Karnaugh maps, and standard building blocks (half and full adders, decoders, encoders, multiplexers).

Counters and shift registers: the ripple (asynchronous) counter, the synchronous counter, modulo-n counting and resetting, and serial and parallel shift registers.

Logic gates and Boolean algebra: the gates AND, OR, NOT, NAND, NOR, XOR and their truth tables, Boolean expressions, the laws of Boolean algebra, De Morgan's laws, and universal gates.

Sequential logic: the difference from combinational logic, the SR latch, the clocked D-type and JK flip-flops, edge triggering, and the flip-flop as a one-bit memory.

Assembly language programming: instructions and registers, reading inputs and writing outputs, branching and loops, delays, and the program development cycle (flowchart, code, assemble, test).

Microcontroller architecture: the CPU, memory and input/output ports, digital input and output pins, pull-up and pull-down resistors, and the analogue-to-digital converter and PWM peripherals.

System design and realisation: the systems approach (input, process, output and power subsystems), block diagrams, systematic testing and fault-finding, evaluation against a specification, and health and safety.

Interfacing a microcontroller: input interfacing (signal conditioning, switch debouncing, the ADC), output interfacing (transistor and MOSFET drivers, relays, motor control with PWM and an H-bridge), and the closed-loop control system.

Transistors: the bipolar junction transistor as a current amplifier with current gain, the MOSFET as a voltage-controlled device, the common-emitter amplifier, and biasing.

Diodes and rectification: the diode characteristic and forward voltage, light-emitting and Zener diodes, half-wave and full-wave (bridge) rectification, and reservoir smoothing.

High power switching systems: relays and the flyback diode, power MOSFETs, the thyristor and triac for AC loads, and pulse-width modulation for power control.

Mains power supply systems: the transformer, rectifier, reservoir smoothing and regulation stages, ripple voltage, and series and switch-mode regulators.

Transistor switching: saturation and cut-off, choosing the base resistor, the Darlington pair, and driving output transducers such as lamps, LEDs, buzzers and motors.

Analogue-to-digital conversion: sampling, quantisation and resolution, the sampling theorem and aliasing, quantisation error, and the trade-off between resolution and data rate.

Digital-to-analogue conversion: the summing-amplifier (binary-weighted) DAC, the R-2R ladder, resolution and the analogue output, and reconstruction filtering.

Communications and wireless transmission: the need for a carrier, amplitude and frequency modulation, bandwidth, digital modulation (ASK, FSK), and the radio transmitter and receiver chain.

Digital communications: serial and parallel transmission, the data rate (bit rate and baud), multiplexing (time-division and frequency-division), and error detection with parity and checksums.

Optical communication: the optical link (LED or laser source, fibre, photodiode receiver), total internal reflection, attenuation and bandwidth, and the advantages over copper.