Why common emitter configuration is widely used

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Welcome back. Continue with Google Continue with email. CE configuration is popular in amplifier circuits. Please log in to add an answer. This is because for higher fixed values of output voltage, the cut in voltage is increased above 0.

Therefore, to overcome this cut in voltage, more input voltage V BE is needed than previous case. The output characteristics describe the relationship between output current I C and output voltage V CE. The output current or collector current I C is taken along y-axis vertical line and the output voltage V CE is taken along x-axis horizontal line. For each level of output voltage, the corresponding output current I C is recorded.

In this region, both junctions are reverse biased. This region is known as the active region of a transistor. In this region, emitter-base junction is forward biased and the collector-base junction is reverse biased. This steps are repeated for higher fixed values of input current I B I. When output voltage V CE is reduced to a small value 0. As we know that the emitter-base junction is already forward biased. Therefore, when both the junctions are forward biased, the transistor operates in the saturation region.

In this region, a small increase in output voltage V CE will rapidly increases the output current I C. Dynamic input resistance is defined as the ratio of change in input voltage or base voltage V BE to the corresponding change in input current or base current I B , with the output voltage or collector voltage V CE kept at constant. In CE configuration, the input resistance is very low. In CE configuration, the output resistance is high.

Again this varies considerably upon the electronic component values chosen and current levels permitted. However if current drain allows higher current levels to be drawn, the output impedance can be reduced considerably.

The level of resistance or impedance comes from the fact that the output is taken from the collector where there is a reverse-biased junction. Another important factor to be considered at the outset of the electronic circuit design is the gain level that can be achieved.

There are two forms of gain that can be determined: current gain and voltage gain. This is the ratio of collector current to base current. This may be thought of as the ratio of output current to input current.

To gain an accurate figure of the gain for a signal, the current gain for small input changes in current is often used. In order to look at the voltage gain of the common emitter amplifier circuit, it is necessary to look at the resistances or impedances for the input and output. The reason for this can be seen from the fact that as the input voltage rises, so the current increases through the base circuit. In turn this increases the current thought the collector circuit, i.

This results in the voltage between the collector and emitter terminals falling. In this way an increase in voltage between the base and emitter has resulted in a fall in voltage between the collector and emitter terminals, in other words the phase of the two signals has been inverted.

When undertaking electronic circuit design for various applications and to meet various requirements, it is possible to use one of a variety of variants of the common emitter transistor circuit. While the basic theoretical circuits shown above are able to describe the basic operation of the common emitter amplifier in concept.

However, for the circuit to be able to operate in a real system, other elements such as bias, decoupling and the like need to be added. As a result, the overall circuit for a common emitter amplifier utilises several components to ensure that it is able to operate in the fashion required.

The first example is the simplest form of common emitter circuit, using very few electronic components. It is typically used for driving a load from a digital output from the previous stage.