Understand Electronics, 2nd Edition

19

Logic circuits

Whether we are reading the time on a digital watch, dialling a call on a mobile phone, listening to a compact disc, using a Smartcard, or sending an e-mail, we are using logic circuits. More and more of the equipment we use at home and at work depend on electronic logic. Logic is the science of reasoning, and we use its electronic equivalent as the basis for a whole host of so-called ‘intelligent’ devices.

The form of logic most suitable for implementing electronically is binary logic. In binary logic, we deal with only two states. A statement is true or it is untrue: there are no half-truths. A digit is 1 or 0: there are no fractions or other values. A transistor is either fully on (saturated) or fully off: it switches rapidly ...