If some percentage of an amplifier’s output signal is connected to the input, so that the amplifier amplifies part of its own output signal, we have what is known as feedback. Feedback comes in two varieties: positive (also called regenerative), and negative (also called degenerative). Positive feedback reinforces the direction of an amplifier’s output voltage [...]
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Transistor as a switch
Because a transistor’s collector current is proportionally limited by its base current, it can be used as a sort of current-controlled switch. A relatively small flow of electrons sent through the base of the transistor has the ability to exert control over a much larger flow of electrons through the collector. Suppose we had a [...]
AMPLIFIERS3
Transistor:Input and output coupling
To overcome the challenge of creating necessary DC bias voltage for an amplifier’s input signal without resorting to the insertion of a battery in series with the AC signal source, we used a voltage divider connected across the DC power source. To make this work in conjunction with an AC input signal, we “coupled” the [...]
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The common-base amplifier
The final transistor amplifier configuration (Figure below) we need to study is the common-base. This configuration is more complex than the other two, and is less common due to its strange operating characteristics. Common-base amplifier It is called the common-base configuration because (DC power source aside), the signal source and the load share the base [...]
Article5
The common-collector amplifier
Our next transistor configuration to study is a bit simpler for gain calculations. Called the common-collector configuration, its schematic diagram is shown in Figure below. Common collector amplifier has collector common to both input and output. It is called the common-collector configuration because (ignoring the power supply battery) both the signal source and the load [...]
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Transistors : The common-emitter amplifier
At the beginning of this chapter we saw how transistors could be used as switches, operating in either their “saturation” or “cutoff” modes. In the last section we saw how transistors behave within their “active” modes, between the far limits of saturation and cutoff. Because transistors are able to control current in an analog (infinitely [...]
Article7
Resistor ( how to read the resistor’s band )
Resistor is a two-channel electronic components designed to withstand an electric current by producing a voltage drop between the two channels in accordance with current, based on Ohm’s law: Resistor is used as part of electrical networks and electronic circuits, and is one of the most frequently used components. Resistors can be made from various [...]
