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Common collector amplifier current gain in transistors

Any transistor has three terminals, the emitter , the base , and the collector. Using these 3 terminals the transistor can be connected in a circuit with one terminal common to both input and output in three different possible configurations. In every configuration, the emitter junction is forward biased and the collector junction is reverse biased. The name itself implies that the Base terminal is taken as common terminal for both input and output of the transistor.


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WATCH RELATED VIDEO: Common Collector and Common Base Amplifiers

BJT Common Collector Amplifier


The figure shows the transistor connected in common emitter configuration and the figure also shows the hybrid equivalent circuit of such a transistor. In common emitter transistor configuration, the input signal is applied between the base and emitter terminals of the transistor and output appears between the collector and base terminals. The input voltage V bc and the output current i c are given by the following equations:. Where r L is the A. C load resistance. Its value is equal to the parallel combination of resistance R E and R C.

Since h fe of a transistor is a positive number, therefore A i of a common emitter amplifier is negative. The resistance looking into the amplifier input terminals i. The input resistance of the amplifier stage called stage input resistance R is depends upon the biasing arrangement.

For a fixed bias circuit, the stage input resistance is,. Since the current gain A i of a common base amplifier is positive, therefore the voltage gain A v is also positive. It means that there is no phase difference between the input and output signals of the common base amplifier.

The voltage gain, in terms of h-parameters, is given by the relation. Calculate the values of input resistance, output resistance, current gain and voltage gains of the amplifier stage. Main menu. Input Resistance The resistance looking into the amplifier input terminals i. Log in to post comments. Search Search.


What is Common Collector Amplifier : Characteristics and Its Applications

Basically it is required to have four terminals so that two are preferred for the input and the remaining two is for output side. But it has only three terminals named as collector, base and the emitter. Among these terminals one is made common so that it can be connected on both sides of input as well as output. This leads to the formation of three configurations that are common base, common collector and the common emitter. Each configuration based on its voltage and the current gains is utilized for respective specifications.

6. Among BJT amplifiers, common-emitter amplifier is most favoured. Give reasons. 7. What is an emitter follower? Discuss its main.

Common Collector Amplifier


The Web This site. Because an amplifier must have two input and two output terminals, a transistor used as an amplifier must have one of its three terminals common to both input and output as shown in Fig 3. The choice of which terminal is used as the common connection has a marked effect on the performance of the amplifier. A transistor connected in the three modes illustrated in Figs. These differences can be exploited by the circuit designer to give an amplifier with characteristics that are most suited a particular purpose. Note that the diagrams are shown here reduced to their most basic form and are not intended to be practical circuits. In a transistor amplifier circuit, such as those shown in Figs. This is because, although there is obviously a voltage the supply voltage between these two points, the DC supply is always de-coupled by a large capacitor e. To give VOLTAGE amplification, a load resistor or an impedance such as a tuned circuit must be connected in the collector circuit, so that a change in collector current causes a change in the voltage developed across the load resistor. This is because the larger the load resistor, the larger the change in voltage that will be caused by a given change in collector current.

Common collector configuration of transistor [detailed explanation]

common collector amplifier current gain in transistors

In the given circuit, since the base current is negligible, so the base voltage V B can be found out by using a voltage divider rule as:. The output voltage will not be distorted until the transistor enters the saturation region. Where V CE is the collector to emitter voltage difference when the transistor is operating in the linear region. Start Learning. This question was previously asked in.

The picture on the left shows the schematic of the common-collector circuit with an NPN transistor. The picture on the right shows the schematic of the common-collector circuit with a PNP transistor.

Module 3.6


Hello friends, I hope you all are doing great. It is another category of BJT amplifier configuration in which input voltage is given at the base and output is taken at the emitter of the transistor. While collector is common between base and emitter terminals. Such type of arrangement is known as a common collector because the collector is linked with the ground. Thanks for reading.

In a common collector amplifier the voltage gain is

The amplifier is an electronic circuit that is used for amplifying a voltage or current signal. The input for the transistor will be a voltage or current and the output will be an amplified form of that input signal. An amplifier circuit is generally designed with one or more transistors is called a transistor amplifier. In this article, we will discuss the common-collector amplifier circuit. The Transistor amplifiers are most commonly using in our day to day life applications like an audio amplifier, Radio Frequency, audio tuners, Optical fiber communication , etc. As we discussed in our previous article, there are three transistor configurations that are used commonly for signal amplification i. Good transistor amplifiers essentially have the following parameters high gain, high input impedance, high bandwidth, high slew rate, high linearity, high efficiency, high stability, etc. In the Common Collector transistor configuration, we use the collector terminal as common for both input and output signals.

three terminal device forming the basis of a Bipolar Transistor, or BJT for short Common Collector Configuration - has Current Gain but no Voltage Gain.

Electronic devices: BJT Amplifiers [part 2]

Basically it is required to have four terminals so that two are preferred for the input and the remaining two is for output side. But it has only three terminals named as collector, base and the emitter. Among these terminals one is made common so that it can be connected on both sides of input as well as output. The configuration of the common collector is also known as emitter follower because of its dependence on emitter terminal and its currents.

Transistor Configurations

RELATED VIDEO: Video 9 - Common collector amplifier design

The quiescent collector current I C , of a transistor is increased by changing resistances. As a result. Answer: C. All capacitances are large.

Here we cover topics — common collector configuration of the transistor — circuits, characteristics, applications, disadvantage, why it is called emitter-follower circuit?

The common-collector CC amplifier is usually referred to as an emitter-follower EF. The input is applied to the base through a coupling capacitor, and the output is at the emitter. The voltage gain of a CC amplifier is approximately 1, and its main advantages are its high input resistance and current gain. An emitter-follower circuit with voltage-divider bias is shown in FIG. Notice that the input signal is capacitively coupled to the base, the output signal is capacitively coupled from the emitter, and the collector is at ac ground.

The term amplifier as used in this chapter means a circuit or stage using a single active device rather than a complete system such as an integrated circuit operational amplifier. An amplifier is a device for increasing the power of a signal. This is accomplished by taking energy from a power supply and controlling the output to duplicate the shape of the input signal but with a larger voltage or current amplitude. In this sense, an amplifier may be thought of as modulating the voltage or current of the power supply to produce its output.




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