![]() ![]() 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.Due to this biasing current, 2N3904 goes to the saturation state and the LED turns ON.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. When the switch is closed, the base of the transistor is biased, and current flows to the base of the transistor. Due to this, 2N3904 remains in the cut-off state and the LED does not glow. ![]() And no current flows to the base of the transistor. When the switch is open, the base of the transistor is not biased. The required resistor value can be easily calculated using Ohm’s law. Proper biasing of the base ensures adequate base current to turn ON the transistor.Ī resistor of 220 Ohm is connected between the load(LED) and the collector terminal to protect the LED from overcurrent. The base of the transistor is biased using a 10 K Ohm resistor(R3) in parallel to the 1 K Ohm resistor(R2) plus base-emitter junction resistance(in series). The complete circuit is powered via a 5 V supply. In the circuit diagram given above, 2N3904 is used as a switch to turn ON/OFF an LED connected at the collector terminal. ![]()
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