The BC557 PNP General Purpose Transistor is the essential counterpart to the BC547, forming the backbone of many complementary circuit designs. At Electrapac, we recommend this transistor for engineers and students in Bangladesh who need a reliable, low-power switch or amplifier for "high-side" switching applications.

Product Overview

The BC557 is a Positive-Negative-Positive (PNP) bipolar junction transistor (BJT) housed in the standard TO-92 package. While an NPN transistor (like the BC547) is typically used to connect a load to ground, the PNP BC557 is perfectly suited for connecting a load to the positive supply rail. It is a staple component for audio pre-amplifiers, oscillator circuits, and signal processing.

Key Features for Electrapac Customers

• Complementary Pair: The BC557 is the direct PNP match for the NPN BC547. Using them together allows you to build Push-Pull amplifiers and Class B output stages.

• High Gain Range: Available in different gain grades (A, B, and C), providing the flexibility to handle everything from simple switching to sensitive signal amplification.

• Low Voltage & Current: Optimized for low-power battery-operated devices, ensuring minimal energy loss in your DIY projects.

• Standard TO-92 Footprint: Its small size and industry-standard pinout make it compatible with almost all breadboards and prototype PCBs available at Electrapac.

• Robust Thermal Stability: Designed to operate reliably across a wide temperature range, making it suitable for the varied environmental conditions in Bangladesh.

Pinout & Connection Guide

When looking at the flat side of the BC557 with the pins pointing downwards, the pinout is:

1. Pin 1 (Left): Collector (Connects to the Load/Ground side).

2. Pin 2 (Middle): Base (The control trigger; for PNP, pulling this LOW turns the transistor ON).

3. Pin 3 (Right): Emitter (Connects to the Positive Supply rail).

Pro-Tip: Remember that a PNP transistor works differently than an NPN. To turn the BC557 ON, the Base voltage must be lower than the Emitter voltage. This makes it excellent for "High-Side" switching where you want to control the power flowing into a component.

Primary Applications

• High-Side Switching: Controlling the positive power supply to a module or LED.

• Push-Pull Amplifiers: Working alongside the BC547 to drive speakers or small motors efficiently.

• Current Mirrors: Used in analog circuit design to create constant current sources.

• Signal Inversion: Flipping a logic signal from High to Low or vice versa.

• Oscillator Circuits: Building LED flashers, sirens, and tone generators.

Why Shop at Electrapac?

We source our BC557 PNP Transistors to ensure consistent gain and breakdown voltage, providing our customers with professional-grade components for their repairs and innovations. Visit us at for the discrete semiconductors that keep your circuits running smoothly.