ELEC 241 Lab

Introduction

In Lab 3 we saw that the voltage divider was an attenuator: $v_{out} = \frac{R_2}{R_1 + R_2} v_{in} = A v_{in}$ , where $A \le 1$ . If we had a box where $v_{out} = A V_{in}$ with $A > 1$ we would have an amplifier. To be more precise, we would have a non-inverting, voltage amplifier. If $A < -1$ we would still be increasing the magnitude of the signal, but would change its sign. This is called an inverting amplifier. We could also have a current amplifier where $i_{out} = A_i i_{in}$ .

Circuits containing only resistors, capacitors, and inductors (e.g. attenuators or RC filters) are passive. An amplifier is an active circuit element: it delivers more power to its load than it receives from its source. (In fact this additional power comes from an external power supply, so no laws of physics are being violated, but when we're drawing circuit diagrams we usually draw only the amplifier and ignore the power supply.)