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BC557 PNP Transistor | BC557 Transistor as An Amplifier

BC557 transistor is switched off the current would be present at the base terminal otherwise there will be no flow of current at that very terminal.
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BC557 PNP Transistor | BC557 Transistor as An Amplifier

bc557 transistor project - Electronic Project


The BC557 is a famous three-terminal semiconductor device used to switch or amplify electrical power supply & electronic signals in electronic circuits. It is a bipolar junction of the transistor (BJT) that falls under the family of PNP transistors i.e. one N-doped layer for the stands between the two P-doped layers. This is a general purpose of the transistor available in a tiny package like TO-92. The BC557 has an hFE rating range from 125 to 800 which makes it an ideal transistor to use as a small signal amplifier in electronic circuits diagram. The HFE ratings are determined by the last letter after the transistor of the number, for example, for the BC557A transistor hFE ratings are 110-220, for the BC557B transistor it is 200-450 hFE or for the BC557C transistor, it is 420-800 hFE. Another good feature of this transistor is the maxi-collector dissipation is 500 milliwatts. The maximum collector current flow of this transistor is 100mA i.e. we could drive loads of a maximum of 100mA through the transistor.

BC557 is a bipolar junction of the transistor that falls under the family of PNP transistors.As this is a PNP transistor, there will be no current flow at the base terminal when the transistor is turned ON and in that case, both the emitter and collector will be forward-biased. When voltage is applied at the base of the terminal, the transistor is turned OFF or both the emitter and collector will be reverse-biased.It carries three terminals called collector, base, and emitter which are commonly used for external connection with the electronic circuit diagram.All these terminals are different in terms of their size or doping concentration. The emitter is highly doped against both the collector and emitter of the terminals.

BC557 contains two layers i.e. two p-doped layers or one n-doped layer. Then-doped layer lies between the 2-doped layers. Here the base terminal is negative while the emitter or collector will be positive.The maximum collector current flow is 100mA indicating we cannot drive loads through the transistor that utilizes more than 100mA current flow. It is mainly used for amplification purposes. Amplification is the process by which a transistor boosts the small input voltage into a large output of the voltage i.e. small audio signal would be amplified into a large audio signal.

Diagram of BC557 Transistor Pin:

bc557 transistor project

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Working Principle of [Related Title]:

PNP transistors have a very similar schematic of the symbols to that of an NPN transistor. However, the only difference between the NPN or PNP symbols is the direction of the arrow on the emitter. In the case of the PNP transistor, the point of the arrow is inward, whereas, in the NPN, the point of the arrow is outward. Generally, the BC557 transistors have two types of symbols that are used in different schematic/circuits.

A transistor is a device the consisting of two P-N Junction diodes connected back-to-back. In PNP transistors, one n-type semiconductor is doped with 2- p-type semiconductors; whereas in NPN transistors, one p-type material is placed between two n-type materials.BC557 is a PNP BJT Transistor; in which the majority of carriers are holes. It has two working states, one is Forward Bias and the other is Reverse Bias. In forward bias, BC557 works as a switch, or the same transistor works as an amplifier in reverse bias. This is a current flow-controlled transistor in which only a small amount of current flow is present in the base terminal that is used to control the large current flow present in the other two remaining terminals.

There is a point to be noted that when our BC557 transistor is switched off the current flow would be present at the base terminal otherwise there will be no flow of current flow at that very terminal i.e., the flow of current flow would not be there when the transistor would be switched on.BC557 is a PNP transistor. When this transistor is used as a switch, it is operated in the Saturation or cut-off region. The transistor acts as an open switch during forwarding bias conditions and acts as a closed switch during reverse bias of the conditions. We could obtain this biasing by providing the necessary amount of current flow toward the base terminal (the maximum biasing current flow that is allowed is 5 mA). If we take the current value more than the max. biasing current flow then it may damage our transistor.

As previously mentioned, the BC557 of the transistor functions like an amplifier when it is reverse-biased. This transistor may use different configurations namely, Common collector, Common base, or Common emitter to amplify current, voltage, or power supply. But, among all the configurations mentioned above the most generalized one is the common emitter of the configuration. While using the said transistor as an amplifier there is a DC current flow gain which could be measured with the help of the given formulae.

The BC557 is a widely used of PNP bipolar junction transistor manufactured in a small TO-92 package. It is a general-purpose PNP transistor that could be used as a switch or amplifier in an electronic circuit diagram. Its HFE ratings are 125 to 800, which makes it an ideal transistor to use as a small signal amplifier in electronic circuit diagrams such as audio signal amplification. The max collector of the dissipation is 500 milliwatt which makes it suitable to use in amplification stages. Moreover, it would also perform well when used as a switch for loads under 100mA. The transistor has also a good collector-to-emitter (VCE) value that is -45V, therefore you can easily use it in a circuit diagram using 40 to 45 volts DC.

Frequently Asked Questions

What is a BC 547 transistor?

BC547 is a bipolar junction of the transistor (BJT). It is a kind of the NPN transistor. It has 3-terminals: Emitter, Collector, and Base. The maximum current flow gain of BC547 is 800A.

What is the use of the BC557 transistor?

BC557 is a general-purpose transistor, used as an amplifier or a switch in electronic circuits diagram. Its hFE ratings of this transistor range from 125 to 800 to make the transistor ideal by using an amplifier within an electronic circuits diagram like audio signal amplification.

What is the material of the BC557 transistor?

BC557 is a semiconductor device used to amplify or switch electronic signals and electrical power supply. It is composed of semiconductor material usually with at least three terminals for connection to an external circuit diagram.

Is BC547 positive or negative?

A BC547 of the transistor is a negative-positive-negative (NPN) transistor that is used for many purposes. Together with other electronic components, such as resistors, coils, or capacitors, it could be used as the active component for switches and amplifiers.

What type is BC557?

A Transistor acts as an Amplifier when operating in an Active of the Region. It can amplify power, voltage, and current flow in different configurations.

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