Logic gates and circuits: transistors as switches, half-adders and adders

This week’s topics

Logic gates and circuits: transistors as switches, half-adders and adders

1. Transistors as switches and MOSFETs
2. Implementing logic operations in circuits
3. Half-adders and adders built from logic gates in Verilog

What you will be able to do

• 4.3 Explain how logical operations are implemented using transistors in electronic circuits.
• 4.4 Explain how complex arithmetic operations can be built up from basic logic.
• 4.5 Implement basic arithmetic operations using logic gates.

Activity

Start with this week’s 4 videos, then: Seminar, guided reading and a short written task: explain how logical operations are implemented using transistors in electronic circuits.

Study materials

Videos

• Creating logic circuits · Oak National Academy, Key Stage 4 (GCSE level) · for registered students
• Constructing Truth Tables for Combinational Logic Circuits · YouTube · Engineers Academy · 10 min · for registered students
• Understanding Logic Gates · YouTube · Spanning Tree · 7 min · for registered students
• Everything about Logic Gates in 12 Minutes | AND, OR, NOT, NOR, NAND, XOR, XNOR Gates · YouTube · Brain Station Advanced · 12 min · for registered students

Further resources

• The Elements of Computing Systems, ch. 2: Boolean Arithmetic · PDF · Nisan & Schocken, The Elements of Computing Systems 2e, ch. 2 (2nd ed.): half adders and full adders as simple logic circuits; 12 pp. · for registered students
• A symbolic analysis of relay and switching circuits · Open-access article · Shannon (1938), Transactions of the AIEE (MIT thesis version). The classic showing that switching circuits follow Boolean algebra. · for registered students