transistor base emitter collector current

Applications I: Switches - Application circuits showing how transistors are used as electronically controlled switches.Operation Modes - An overview of the four possible operating modes of a transistor.Extending the Water Analogy - Going back to the water analogy to explain how a transistor acts like a valve.Symbols, Pins, and Construction - Explaining the differences between the transistor's three pins.

This tutorial is split into a series of sections, covering: We won't dig too deeply into semiconductor physics or equivalent models, but we'll get deep enough into the subject that you'll understand how a transistor can be used as either a switch or amplifier. Covered In This TutorialĪfter reading through this tutorial, we want you to have a broad understanding of how transistors work. In quantities of thousands, millions, and even billions, transistors are interconnected and embedded into tiny chips to create computer memories, microprocessors, and other complex ICs. If you are designing a PCD or Perf board with this component then the following picture from the Datasheet will be useful to know its package type and dimensions.In small, discrete quantities, transistors can be used to create simple electronic switches, digital logic, and signal amplifying circuits. Amplifier modules like Audio amplifiers, signal Amplifier etc.Driver Modules like Relay Driver, LED driver etc.When uses as an Amplifier the DC current gain of the Transistor can be calculated by using the below formulaeĭC Current Gain = Collector Current (I C) / Base Current (I B) Of the above types common emitter type is the popular and mostly used configuration. Some of the configurations used in amplifier circuits are It can amplify power, voltage and current at different configurations. The value of I B should not exceed mA.Ī Transistors acts as an Amplifier when operating in Active Region. Where, the value of V BE should be 5V for BC547 and the Base current (I B depends on the Collector current (I C). The value of this resistor (R B) can be calculated using below formulae.

Anything more than 5mA will kill the Transistor hence a resistor is always added in series with base pin. As mentioned the biasing current should maximum of 5mA. As discussed a transistor will act as an Open switch during Forward Bias and as a Closed switch during Reverse Bias, this biasing can be achieved by supplying the required amount of current to the base pin. When a transistor is used as a switch it is operated in the Saturation and Cut-Off Region as explained above. When base current is removed the transistor becomes fully off, this stage is called as the Cut-off Region and the Base Emitter voltage could be around 660 mV. This stage is called Saturation Region and the typical voltage allowed across the Collector-Emitter (V CE) or Base-Emitter (V BE) could be 200 and 900 mV respectively. When this transistor is fully biased then it can allow a maximum of 100mA to flow across the collector and emitter. To bias a transistor we have to supply current to base pin, this current (I B) should be limited to 5mA. The maximum amount of current that could flow through the Collector pin is 100mA, hence we cannot connect loads that consume more than 100mA using this transistor. Note: Complete Technical Details can be found at the BC547 datasheet given at the end of this page.īC549, BC636, BC639, 2N2222 TO-92, 2N2222 TO-18, 2N2369, 2N3055, 2N3904, 2N3906, 2SC5200īC547 transistor has a gain value of 110 to 800, this value determines the amplification capacity of the transistor.

Continuous Collector current (I C) is 100mA.

BC547 is a NPN transistor hence the collector and emitter will be left open (Reverse biased) when the base pin is held at ground and will be closed (Forward biased) when a signal is provided to base pin.

Transistor base emitter collector current