What type of transistor is in an amplifier

In this tutorial, we will learn about the classification and different Types of Transistors. Transistor is a semiconductor device which is used to either amplify the signals or to act as an electrically controlled switch. Since a long time, the vacuum tubes are replaced with transistors because the transistors have more benefits over vacuum tubes.

Transistors are small in size and it requires low energy for operation and also it has low power dissipation. The Transistor is one of the important active components a device which can produce an output signal higher power than that in the input signal. From the time of invention of the first transistor to the present day, transistors are classified into different types depending either on their construction or their operation.

The following tree diagram explains a Basic Classification of different Transistor types. The classification of transistors can be easily understood by observing the above tree diagram.

Transistors are basically classified into two types. Again, depletion and enhancement mode transistors are further classified into respective N—Channel and P—Channel.

Commonly used semiconductor materials for manufacturing transistor are Silicon, Germanium and Gallium-Arsenide. Basically, the transistors are classified depending on their structure. Each type of transistors has their own characteristics, advantages and disadvantages. Physically and structurally speaking, the difference between BJT and FET is that in BJT both majority and minority charge carriers are required to operate, whereas in case FETs, only majority charge carriers are required. Based on their properties and characteristics, some transistors are primarily used for switching purpose MOSFETs and on the other hand, some are transistors are used for amplification purpose BJTs.

Some transistors are designed for both amplification and switching purposes. BJTs are essentially current-controlled devices. If small amount of current flows through the base of a BJT transistor, then it causes a flow of large current from emitter to collector. The Bipolar Junction Transistors have low input impedance and it causes to flow large current through the transistor.

The Bipolar Junction Transistors are only turned ON by the input current, which is given to the base terminal. BJTs can operate in three regions. They are:. The NPN transistor consists of two n-type semiconductor materials and they are separated by a thin layer of p-type semiconductor.

Here, the majority charge carriers are electrons while holes are the minority charge carriers. The flow of electrons from emitter to collector is controlled by the current flow in the base terminal. But common emitter configuration is frequently used in the applications like an audio amplifier. With the help of the following transistor amplifier circuit, one can get an idea about how the transistor circuit works as an amplifier circuit.

In the below circuit, the input signal can be applied among the emitter-base junction and the output across the Rc load connected in the collector circuit. For accurate amplification, always remember that the input is connected in forward-biased whereas the output is connected in reverse-biased.

For this reason, in addition to the signal, we apply DC voltage VEE in the input circuit as shown in the above circuit. Generally, the input circuit includes low resistance as a result; a little change will occur in signal voltage at the input which leads to a significant change within the emitter current.

Because of the transistor act, emitter current change will cause the same change within the collector circuit. At present, the flow of collector current through an Rc generates a huge voltage across it. Therefore, the applied weak signal at the input circuit will come out in the amplified form at the collector circuit in the output. The low resistance in input circuit, lets any small change in input signal to result in an appreciable change in the output. The emitter current caused by the input signal contributes the collector current, which when flows through the load resistor R L , results in a large voltage drop across it.

Thus a small input voltage results in a large output voltage, which shows that the transistor works as an amplifier. Let there be a change of 0. This emitter current will obviously produce a change in collector current, which would also be 1mA.

Hence it is observed that a change of 0. As the common emitter mode of connection is mostly adopted, let us first understand a few important terms with reference to this mode of connection. As the input circuit is forward biased, the input resistance will be low. There are three types on the basis of Method of coupling. There are several transistors available in the market as per different applications.

The important types are as follows. Electrons, as well as the holes, act here as charge carriers. In the PNP configuration, the transistor P junction has many holes, and the intermediate junction called N has efficiency and electrons. Now, the EB junction becomes the reverse biased and the CB junction becomes revere bias. Due to the connection the bias formed and the holes started flowing from P junction. After that, the flow continues towards the N region.