ELEC 240 Lab

Introduction

In Lab 3 we saw that the voltage divider was an attenuator:

\[ v_{out} = \frac{R_2}{R_1 + R_2} v_{in} = G v_{in} \]

where \(G \le 1\). Let's consider a blackbox with an input voltage \(v_{in}\) and an output voltage \(v_{out}\) = G v_{in}$ with \(G > 1\). This black box would be an amplifier. To be more precise, we would have a non-inverting, voltage amplifier. If \(G < -1\), we would still be increasing the magnitude of the signal, but would invert its sign. This is called an inverting amplifier.

Similarly, a current amplifier would be described as \(i_{out} = G_i i_{in}\). Circuits containing only resistors, capacitors, and inductors are passive. An amplifier is an active circuit element; it delivers more power to its load than it receives from its source. This additional power comes from an external power supply, so no laws of physics are being violated, but when we are drawing circuit diagrams we usually only draw the amplifier and ignore the power supply.