BC557 transistor is a PNP bipolar junction general-purpose transistor that is used as a switch or amplifier in electronic circuits. It has 125 to 800 HFE ratings which make it an ideal transistor to use as a small signal amplifier in electronic circuits. The maximum collector dissipation is 500 milliwatts which are also another good feature of this transistor. Moreover, its performance well when used it as a switch for load under 100mA. BC557 transistor has also good collector to emitter (VCE) value that is -45V, therefore you can easily use it in circuits using 40 to 45 volts DC.
Besides these uses, BC557 is also a good general-purpose PNP transistor to use in your simple electronics projects so this transistor has to have in your electronics lab.
- Max voltages Collector-Emitter: -45 V
- Maximum Collector-Base Voltage: -50 V
- Max Emitter-Base Voltage: -5 V
- Collector Current: -0.1 A
- Collector Dissipation – 0.5 W
- Current Gain (hfe) – 110 to 800
- Frequency of BC557 – 150 MHz
- 2 dB Noise Figures
- Operating Temperature Range -65 to +150 °C
- TO-92 Package
PNP Complementary of BC557 Transistor:
BC 557 is an NPN transistor so its Complementary is BC547
Replacement and Equivalent:
The alternative of this transistor is 2N3906, 2N4403, BC556, BC327. Keep in min the output pins of some equivalents are different So please see pinout details of the equivalent transistor before replacing in the circuit.
Applications of BC557 Transistor:
- BC557 is used in the preamplifier
- It is also used in small signal audio amplifier
- It is also used in Driving Loads under 0.1mA or 100mA
- This transistor widely used PNP transistor so it can be used in Any general-purpose application that comes under its ratings
How to protect Transistor BC557:
For the long life of this transistor it is essential to not operate it under -45V DC in your electronic circuits, always use a suitable resistor on-base point, do use this transistor more than -100mA load, the operating and storage temperature. The temperature should be under -65 to +150 Centigrade, and always check the pinout of the transistor before placing it in By chance wrongly placed, then check the transistor again before placing it in the circuit because wrong input can weak its performance.
BC557 As a Switch Circuit:
As we use a transistor as a switch it is operated in Saturation and cut Off region. A transistor acts as an open switch during forwarding bias and closed switch during reverse bias. The maximum base current should be 5mA for BC557 Transistor as mention above in the features. More current than 5mA will kill the Transistor. So a resistor is always added in series with the base pin. The value of the resistor can be calculated by using this formula.
RB = VBE / IB