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# GCSE Index

This is the AQA version closing after June 2019. Visit the the version for Eduqas instead.

# AQA A Level

## Systems and Subsystems

• Systems
built from one or more subsystems
Input
Process
Output
Arrows represents information flows

## Flow Charts

• Flow Chart Symbols
START, INPUT, PROCESS, OUTPUT
DECISION - Yes / No Answers,
LOOP, END
Construct and interpret flowcharts

## Transducers and Signals

• Transducers
Input
Output
• Signals
current or voltage represents information
• Noise
an unwanted signal
reducing noise
• Processes
counting
timing
amplifying
logic
memory
• Analogue and Digital

## Combinational Logic

• Combinational Logic
LOW = 0
HIGH = 1
• Gates
AND, OR, NOT, NAND and NOR
• Truth Tables
up to four gates
up to three inputs
convert a written description into gates

## Analogue Signals

• processors
analogue
digital
converters D to A, A to D
• signals
analogue
digital
• analogue
Audio amplifiers
• Operational Amplifiers
Comparator
One-bit A to D converter
voltage gain (Gv) = Vout / Vin
power bandwidth
• Op Amp Properties
very large input resistance
low output resistance
very large voltage gain
saturates at the supply voltages

## Basic Electronics

• The Basics
Voltage, Volts (V)
Current, Amps (A)
Resistance, Ohms (Ω)
Power, Watts (W)
P = IV        Power = Current x Voltage
Sum circuit voltages
Voltage across parallel components
Current in series circuits
Current sum at a junction
Current flows, only if there is a PD.
Frequency, Hertz, (Hz)
• Ohms Law
R = V / I
• Resistors and Calculations
up to four series resistors
up two parallel resistors
Voltage dividers
Pull up and pull down
• Sine waves
voltage-time graph
current-time graph
peak value
period value
frequency = 1 / time period
RMS calculations
Vpeak = 1.4 x Vrms
Vrms = 0.7 x Vpeak

## Passive Components

• Components
power ratings
current ratings
voltage ratings
tolerance
polarity
selecting suitable components
• Resistors
colour code
BS1852
E24
• Capacitors
Markings
Polarisation

## Diodes

• Diodes
conduct in one direction only
forward voltage drop = 0.7 V
forward-bias
reverse-bias
• Power Supply Rectifiers
half-wave
full-wave
bridge
• Back EMF Diodes
connected across a relay coil or motor
protect the semiconductor
• LED
calculate series resistor
• LDR
has a very high resistance in the dark
resistance decreases when light level increases
• Thermistor
ntc type
resistance decreases if temperature increases

## Audio Entertainment Systems

• Audio Systems
Tuner
Amplifier
Microphone
Loudspeakers
MP3 Player
CD and DVD players
CD and DVD recorders

• The Simple Radio
Block Diagram
Aerial
RF tuned circuit
Demodulator
AF amplifier
Loudspeaker

## Radio Signal Modulation

• Radio Signals and Modulation
Carrier
Information Signal
Amplitude Modulation (AM)
Frequency Modulation (FM)
Compare FM and AM