However, a small signal across the base is enough to make it work. The transistor will not work if a signal (voltage/current) is applied across the collector and emitter but not across the base. The transistor is now in Reverse Bias mode, which means that no current flows through the collector or emitter. The voltage does not apply to the base terminal when the switch is in the open condition. The following formulae can be used to calculate the value of this resistor (Rb). Any current more than 5mA will damage the transistor, hence a resistor is always connected in series with the base pin. The biasing current should be not more than 5 mA. This biasing can be done by providing the required amount of current to the base pin. When we supply current to the transistor's base, it makes a path for the collector current to flow from the base to the emitter.ĭuring Forward Bias, the transistor will act as an Open switch, and during Reverse Bias, it will act as a Closed switch.

When a transistor is used as a switch it is operated in the Saturation and Cut-Off Region. Driver modules for LED, electronic relay.General switching and amplification purposes.We must supply current to the base pin of a transistor to operate it, and this current (IB) should be limited to 5mA. The maximum current that can flow through the Collector pin is 100mA, we can't use this transistor to connect loads that use more than 100mA. The gain value of the BC547 transistor ranges from 110 to 800, and this value determines the transistor's amplification capacity. This transistor is commonly used for amplification of current as well as switching purposes.

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