Operational amplifiers, or op-amps, are perhaps the most common building blocks found in analogue circuits. They can be used to create amplification stages very easily, and many other types of circuit besides. There are very many ‘op-amp cookbooks’ around that give lots of these circuits, so we won’t add to them here. The main purpose of this chapter is to present you with a pair of tables to enable easy selection of resistor values for any desired gain.
We’ll take a moment, however, to state the two rules that govern an op-amp’s behaviour for the purpose of achieving a first-off analysis of their circuits:
1. The input terminals of op-amps draw no current.
2. The output of the op-amp does whatever it can to ...