Transistors are most commonly used for switching and signal boosting or amplification purposes. So the BC557 Transistor is one of them. It is the most popular electronic component used in most electronic equipment. This can be identified by its shape, the black color plastic package with 3 legs. So in this article you will get the complete details about the BC557 transistor.
What is BC557 Transistor?
BC557 is a PNP transistor, means the positive-negative-positive regions are separated and alter its properties. This is a bipolar junction transistor used for the general purpose like signal boosting and switching purposes.
PNP transistor means the voltage is passing through the transistor if the base pin gets a negative voltage. So this will act like a switch.
BC557 Transistor Pinout
This PNP transistor is coming in the package of TO-92. When you are holding the flat side infront of you then the pin configuration of BC557 transistor is as follows:
- Collector (C)
- Base (B)
- Emitter (E)
Collector, The first pin of BC557 is known as the collector pin. This pin is responsible for main current flow when the transistor is in operational mode. In a PNP transistor the current flows from Emitter to collector pin because BC557 is a forward biased transistor.Â
The collector pin can handle the maximum voltage of 45V and the current of 100mA, so don’t feed over voltage to this transistor above the mentioned voltage, this may damage or explode the transistor.
Base, This is the 2nd pin mentioned in the pinout diagram. These pins will decide if the current can pass or not. This is the main switch of this transistor. If any negative voltage is given to the base pin it opens the circuit and passes the current flow from emitter to collector.
Emitter,This is the last terminal of the transistor, pin number 3. The emitter pin provides the charge to the collector through the base. If the base is allowed to give the charge carrier to the collector it will give otherwise not.typically it connects with the ground. The current flow in the PNP transistor will be Emitter to collector when the transistor is in forward bias.
Features and Specifications
- Type: TO-92 PNP transistor
- Collector to Emitter voltage: -45v
- Collector to Base voltage: -50
- Emitter-Base voltage: -5v
- Collector current: 100mA
- DC current gain(Hfe): 800 (varies by diffrent models and manufacturer)
- Frequency: 100Mhz
BC557 Transistor Equivalent
The equivalant to BC557 PNP transistors are BC556, BC558, BC157, 2N3906, 2SA1943, S8550, BD140 and TIP42. check the pinout of these transistors before installing in to the circuit. The complementry pair of BC557 PNP transistor is BC547 NPN.
BC557 Transistor Working
The BC557 transistor works in both cutoff mode and saturation mode in different situations. In Cutoff mode the PNP transistor is in off state. There is no current flowing from Emitter to collector. This happens because the base voltage is higher than the emitter voltage.Â
In Saturation mode, the current flow is happening through emitter to collector because the base voltage is lesser than the emitter voltage. The collector emitter path impedance is reduced and the current can easily pass through.
BC557 Applications
- LED Control
- Relay driver
- DC motor control
- Logic gate interface
- Microcontroller interface
- Temperature control circuit
- Light activated switch
- Voltage level shifter
- Oscillator circuit
Frequently Asked Questions
The BC557 transistor is using for switching the electronics devices or input signal amplification.
No, the BC547 is a NPN transistor and BC557 is a PNP transistor. The BC557 is the complementry pair of BC547 transistor.
The PNP transistor allow the current flow from Emiter to collector, If the base voltage is less than the emitter voltage then the transistor become forward biasing and allow the current flow from Emitter to Collector.
The BC557 transistor is a type of PNP transistor. Using in general purpose like Swiching and small signal amplification.
