![]() ![]() If you are designing a PCD or Perf board with this component, then the following picture from the BC557 Datasheet will be useful to know its package type and dimensions. 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 formulae DC 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 Transistor acts as an Amplifier when operating in Active Region. Where, the value of V BE should be 5V for BC557 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. 2 is wrong, but if 2 works for you then it means you actually built 1 when you thought you built 2 because you got the transistor legs mixed up. 1 and 2 are the same circuit except the transistor is the other way around. 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. Simple explanation: You got the transistor backwards. 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. This is where a PNP transistor differs from a NPN transistor, a Logic state (blue colour) is used to toggle between Ground and Signal Voltage (Emitter-Base Voltage V BE) as shown belowīC557 has a gain value of 110 to 800, this value determines the amplification capacity of the transistor. Note: Complete Technical Details can be found at the BC557 datasheet given at the end of this page.īC157, BC558, 2N3906, 2SA1943, BD140, S8550, TIP127, TIP42īC557 is a PNP transistor hence the collector and emitter will be closed (Forward biased) when the base pin is held at ground and will be opened (Reverse biased) when a signal is provided to base pin.
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