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Common Emitter Amplifier The most common amplifier configuration for an NPN transistor is that of the Common Emitter Amplifier circuit. In the previous introduction to the amplifier tutorial, we saw that a family of curves known commonly as the  Output Characteristic Curves , relate the transistors Collector Current ( Ic ), to its Collector Voltage ( Vce ) for different values of the transistors Base Current ( Ib ). All types of transistor amplifiers operate using AC signal inputs which alternate between a positive value and a negative value so some way of “presetting” the amplifier circuit to operate between these two maximum or peak values is required. This is achieved using a process known as  Biasing . Biasing is very important in amplifier design as it establishes the correct operating point of the transistor amplifier ready to receive signals, thereby reducing any distortion to the output signal. We also saw that a static or DC load line can be drawn ont...

Introduction to the Amplifier An amplifier is an electronic device or circuit which is used to increase the magnitude of the signal applied to its input. Amplifier  is the generic term used to describe a circuit which produces and increased version of its input signal. However, not all amplifier circuits are the same as they are classified according to their circuit configurations and modes of operation. In “Electronics”, small signal amplifiers are commonly used devices as they have the ability to amplify a relatively small input signal, for example from a  Sensor  such as a photo-device, into a much larger output signal to drive a relay, lamp or loudspeaker for example. There are many forms of electronic circuits classed as amplifiers, from Operational Amplifiers and Small Signal Amplifiers up to Large Signal and Power Amplifiers. The classification of an amplifier depends upon the size of the signal, large or small, its physical configuration and how it pr...