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2- Common Emitter Amplifier

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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...
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16- Common Collector Amplifier

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Common Collector Amplifier Common Collector Amplifiers produce an output voltage across its emitter load which is in-phase with the input signal The  Common Collector Amplifier  is another type of bipolar junction transistor, (BJT) configuration where the input signal is applied to the base terminal and the output signal taken from the emitter terminal. Thus the collector terminal is common to both the input and output circuits. This type of configuration is called Common Collector, (CC) because the collector terminal is effectively “grounded” or “earthed” through the power supply. In many ways the common collector configuration (CC) is the reverse of the common emitter (CE) configuration as the connected load resistor is changed from the collector terminal for R C  to the emitter terminal for R E . The common collector or grounded collector configuration is commonly used where a high impedance input source needs to be connected to a low impedance output l...
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3- Common Source JFET Amplifier

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Common Source JFET Amplifier Common Source JFET Amplifier uses junction field effect transistors as its main active device offering high input impedance characteristics. Transistor amplifier circuits such as the common emitter amplifier are made using Bipolar Transistors, but small signal amplifiers can also be made using Field Effect Transistors. These devices have the advantage over bipolar transistors of having an extremely high input impedance along with a low noise output making them ideal for use in amplifier circuits that have very small input signals. The design of an amplifier circuit based around a junction field effect transistor or “JFET”, (N-channel FET for this tutorial) or even a metal oxide silicon FET or “MOSFET” is exactly the same principle as that for the bipolar transistor circuit used for a Class A amplifier circuit we looked at in the previous tutorial. Firstly, a suitable quiescent point or “Q-point” needs to be found for the correct biasing of the ...
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