
Interfacing Logic Outputs to Real-World Loads | GCSE Electronics | WJEC Eduqas (9–1)
Fully Editable Lesson | Specification-Matched | Calculation-Focused
This lesson develops student understanding of how digital logic systems safely drive larger loads in electronic control systems.
Students learn why logic gates cannot directly power motors, heaters, solenoids or relays, and how transistors, MOSFETs, and comparators act as interface devices between low-current logic outputs and high-current actuators.
Designed to match the WJEC Eduqas GCSE Electronics specification, this lesson combines theory, calculation practice, and real-world design tasks to build confidence with driver circuits.
Key Learning Objectives• Recognise the current and voltage limits of logic gate outputs
• Explain why interface circuits are required
• Design transistor and MOSFET driver circuits
• Calculate base resistors using current gain (hFE)
• Understand MOSFET threshold voltage and switching behaviour
• Add protection (flyback) diodes to protect switching devices
• Apply comparator outputs within control systems
• Output current limitations
• Risks of overloading IC outputs
• Voltage and power considerations
• Using NPN transistors as switches
• Base current calculations
• Applying hFE to determine required base current
• Designing correct base resistor values
• Advantages of MOSFETs in switching
• Gate threshold voltage
• High-current applications
• Logic-level MOSFET considerations
• Inductive loads and back EMF
• Flyback diode placement
• Preventing transistor damage
• Conditioning analogue signals
• Creating clean digital outputs
• Threshold switching applications
• Fully editable PowerPoint with circuit diagrams and worked examples
• Step-by-step calculation walkthroughs
• Practice exercises (heater and motor driver design)
• Real-world control system examples
• Assessment questions for consolidation
• Motor control systems
• Heater switching circuits
• Solenoid and relay drivers
• Industrial and domestic control systems
• Directly aligned to WJEC Eduqas GCSE Electronics
• Strong calculation focus to build exam confidence
• Clear progression from theory to design
• Reduces planning time with ready-to-teach materials
• Develops real-world electronic design skills
GCSE Electronics, WJEC Eduqas, Interfacing, Transistor Driver, MOSFET, Comparator, Logic Outputs, Motor Control, Protection Diode, hFE, Base Resistor Calculation
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