The BC547 is a general-purpose NPN bipolar junction transistor (BJT) widely used in low-power amplification and switching applications. It is a versatile and cost-effective component, making it a popular choice for hobbyists, students, and professionals in electronics. The BC547 is known for its reliability, ease of use, and compatibility with a wide range of circuits.
The BC547 transistor has the following key technical specifications:
Parameter | Value |
---|---|
Transistor Type | NPN |
Maximum Collector-Emitter Voltage (VCEO) | 45V |
Maximum Collector-Base Voltage (VCBO) | 50V |
Maximum Emitter-Base Voltage (VEBO) | 6V |
Maximum Collector Current (IC) | 100mA |
Power Dissipation (PD) | 500mW |
DC Current Gain (hFE) | 110 to 800 (varies by model) |
Transition Frequency (fT) | 150 MHz |
Operating Temperature Range | -55°C to +150°C |
Package Type | TO-92 |
The BC547 transistor comes in a TO-92 package with three pins. The pinout is as follows:
Pin Number | Pin Name | Description |
---|---|---|
1 | Collector | Current flows out of this pin in NPN mode. |
2 | Base | Controls the transistor's operation. |
3 | Emitter | Current flows into this pin in NPN mode. |
The pinout of the BC547 (flat side facing you, pins downward) is shown below:
_______
| |
| |
|_______|
| | |
1 2 3
C B E
Determine the Configuration: Decide whether the transistor will be used as a switch or an amplifier.
Base Resistor: Always use a resistor in series with the base pin to limit the base current and prevent damage to the transistor. The value of the resistor can be calculated using Ohm's Law: [ R_b = \frac{V_{in} - V_{BE}}{I_B} ] Where:
Collector Load: Connect the load (e.g., an LED or motor) in series with the collector pin and the power supply.
Power Ratings: Ensure the voltage and current ratings of the transistor are not exceeded.
The following example demonstrates how to use the BC547 to switch an LED on and off using an Arduino UNO.
// Define the pin connected to the BC547 base
const int transistorBasePin = 9;
void setup() {
// Set the transistor base pin as an output
pinMode(transistorBasePin, OUTPUT);
}
void loop() {
// Turn the LED on by sending a HIGH signal to the transistor base
digitalWrite(transistorBasePin, HIGH);
delay(1000); // Keep the LED on for 1 second
// Turn the LED off by sending a LOW signal to the transistor base
digitalWrite(transistorBasePin, LOW);
delay(1000); // Keep the LED off for 1 second
}
Transistor Not Switching Properly
Overheating
No Output Signal
LED Not Lighting Up
Q1: Can the BC547 handle high-power loads?
A1: No, the BC547 is designed for low-power applications with a maximum collector current of 100mA. For high-power loads, consider using a power transistor like the TIP120.
Q2: What is the difference between BC547 and BC548?
A2: The BC547 and BC548 are similar, but the BC548 has a slightly higher maximum voltage rating and is better suited for higher-frequency applications.
Q3: Can I use the BC547 without a base resistor?
A3: No, a base resistor is essential to limit the base current and prevent damage to the transistor.
Q4: How do I test if a BC547 is working?
A4: Use a multimeter in diode mode to check the base-emitter and base-collector junctions. A forward voltage drop of approximately 0.7V indicates a functional transistor.