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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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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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5- Class A Amplifier

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Class A Amplifier Common emitter amplifiers are the most commonly used type of amplifier as they can have a very large voltage gain Common Emitter (CE) amplifiers are designed to produce a large output voltage swing from a relatively small input signal voltage of only a few millivolt’s and are used mainly as “small signal amplifiers” as we saw in the previous tutorials. However, sometimes an amplifier is required to drive large resistive loads such as a loudspeaker or to drive a motor in a robot and for these types of applications where high switching currents are needed  Power Amplifiers  are required. The main function of the power amplifier, which are also known as a “large signal amplifier” is to deliver power, which is the product of voltage and current to the load. Basically a power amplifier is also a voltage amplifier the difference being that the load resistance connected to the output is relatively low, for example a loudspeaker of 4Ω or 8Ω resul...
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