In digital electronics we work with digital signals, as opposed to analogue ones. Where an analogue signal is continuously changing, a digital signal can only be one of a number of values. In most cases this is one of two values, known as **binary**. **Binary **is where we will begin this course, by looking at how this numbering system is the basis of the operation of digital circuits. We will then look at how we can express and analyse digital circuits using a branch of mathematics called **Boolean algebra**. We will then move onto the theory and construction of digital circuits, which I’ve split into two sections: **combinational logic **and **sequential logic**.

**Combinational logic** uses circuits that have an output that is the function of its input. We will look at logic gates, which are a form of combinational logic that is used in many applications, including making sequential logic possible!

**Sequential logic** uses circuits that have an output that is not only dependent on its present input but also its past input. This allows us to build systems that have a memory.

Circuitry often uses a mixture of combinational and sequential logic.

### Combinational logic – Logic gates

### Sequential logic

### Signal conditioning