BC557 PNP Transistor: Pinout, Application, and Datasheet

The BC557 is a widely used PNP bipolar junction transistor manufactured in small TO-92 package. It is a general purpose PNP transistor that can be used as a switch or amplifier in electronic circuits. Its HFE ratings are 125 to 800, which makes it an ideal transistor to use as a small signal amplifier in electronic circuits such as audio signal amplification.

The max collector dissipation is 500 milliwatt which makes it suitable to use in amplification stages. Moreover it will also perform well when used it as a switch for load under 100mA. The 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.

The HFE ratings of BC557 can be determined by the last letter after its number. For example, BC557A HFE ratings are 110-220, BC557B HFE ratings are 200-450 and BC557C HFE ratings are 420-800.

Symbol

Footprint

3D Model

• Package Type: TO-92

• Transistor Type: PNP

• Max Collector Current(IC): -100mA

• Max Collector-Emitter Voltage (VCE): -45V

• Max Collector-Base Voltage (VCB): -50V

• Max Emitter-Base Voltage (VBE): -5V

• Max Collector Dissipation (Pc): 500 Milliwatt

• Max Transition Frequency (fT): 100 MHz

• Minimum & Maximum DC Current Gain (hFE): 125 to 800

• Max Storage & Operating temperature Should be: -65 to +150Centigrade

ON Semiconductor BC557 technical specifications, attributes, parameters and parts with similar specifications to ON Semiconductor BC557.

The BC557 is a general purpose transistor that can be used in a wide variety of general purpose applications. It can be used as an audio amplifier in small radios, electronic buzzers, electronic bells and other sound circuits that require small amplification. Due to the good gain of the BC557, it can also be used in audio preamplifier stages. Furthermore, the BC557 can perform as a switch in electronic applications for 100mA load, it can be used to switch any part of an electronic circuit, other high-power transistors, LEDs, relays etc.

BC557 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. 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 VBE) as shown below

BC557 has a gain value of 110 to 800, this value determines the amplification capacity of the transistor. 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. To bias a transistor we have to supply current to base pin, this current (IB) should be limited to 5mA.

When this transistor is fully biased then it can allow a maximum of 100mA to flow across the collector and emitter. This stage is called Saturation Region and the typical voltage allowed across the Collector-Emitter (V­CE) or Base-Emitter (VBE) could be 200 and 900 mV respectively. 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.

When a transistor is used as a switch it is operated in the Saturation and Cut-Off Region as explained above. 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. As mentioned the biasing current should maximum of 5mA. Anything more than 5mA will kill the Transistor; hence a resistor is always added in series with base pin. The value of this resistor (RB) can be calculated using below formulae.

RB  = VBE / IB

Where, the value of VBE should be 5V for BC557 and the Base current (IB depends on the Collector current (IC). The value of IB should not exceed mA.

A Transistors acts as an Amplifier when operating in Active Region. It can amplify power, voltage and current at different configurations.

Some of the configurations used in amplifier circuits are

• Common emitter amplifier

• Common collector amplifier

• Common base amplifier

Of the above types common emitter type is the popular and mostly used configuration. 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 (IC) / Base Current (IB)

• Preamplifier

• Small signal audio amplifier

• Driving Loads under 0.1mA or 100mA

• Relay Driver and LED driver

• Darlington pair

• Robotics and instrumentation projects

• Used in motors for controlling current

• Low noise input stages of tape recorders

• HI-FI amplifiers

• Signal processing circuits of television receivers

BC557 Package Outline

ON Semiconductor (Nasdaq: ON) is driving energy efficient innovations, empowering customers to reduce global energy use. The company offers a comprehensive portfolio of energy efficient power and signal management, logic, discrete and custom solutions to help design engineers solve their unique design challenges in automotive, communications, computing, consumer, industrial, LED lighting, medical, military/aerospace and power supply applications. ON Semiconductor operates a responsive, reliable, world-class supply chain and quality program, and a network of manufacturing facilities, sales offices and design centers in key markets throughout North America, Europe, and the Asia Pacific regions.

Download datasheets and manufacturer documentation for ON Semiconductor BC557.