Transistor TIP120 (Darlington Power Transistor)

Features:

• High DC gain for amplifying a small base current to a larger collector current.
• High collector-emitter voltage rating of 60V.
• Collector current up to 5A for high-current applications.
• Darlington configuration with a low base current requirement.
• TO-220 package is suitable for mounting on heat sinks.
• Fast switching speed.
• Low saturation voltage for reduced power dissipation.
• Wide operating temperature range: -65°C to 150°C.

Principle of Work:

The TIP120 has two NPN transistors connected in Darlington configuration. A small base current turns on the first transistor, which then drives the second transistor, allowing a much larger current to flow from collector to emitter. It operates as a switch (fully ON or OFF) or as an amplifier controlling current flow. Typical base current to fully turn on is around 5mA, often provided via an Arduino digital pin through a resistor.

Pinout:

1. Base (B): Input pin controlling the transistor switching.
2. Collector (C): Output pin connected to the load.
3. Emitter (E): Ground pin connected to the negative side of the load.

Applications:

1. Motor control – speed and direction of DC motors.
2. Relay control – switching relays on/off.
3. LED brightness control.
4. Audio amplification.
5. Power switching for heaters, pumps, solenoids, and other high-power devices.

Circuit Example:

Connect the motor between the power supply and the collector. The emitter connects to ground. Use a diode across the motor terminals as a flyback diode. The base connects to Arduino pin 9 via a 2.2k resistor.

Library:

No library required.

Example Arduino Code:

int motorPin = 9;  // Motor control pin
int speed = 0;

void setup() {
  pinMode(motorPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  if (Serial.available() > 0) {
    speed = Serial.parseInt();
    speed = map(speed, 0, 100, 0, 255);
    analogWrite(motorPin, speed);
  }
}

This code reads a speed value (0-100) from the serial monitor, maps it to PWM range (0-255), and controls the motor speed accordingly.

Technical Details:

• NPN Medium-power Darlington Transistor
• High DC Current Gain (hFE), typically 1000
• Continuous Collector Current (IC): 5A
• Collector-Emitter Voltage (VCE): 60V
• Collector-Base Voltage (VCB): 60V
• Emitter-Base Voltage (VBE): 5V
• Base Current (IB): 120mA max
• Peak Load Current: 8A
• Package: TO-220

Resources:

• TIP120 Datasheet

Comparisons:

The TIP120 and IRFZ44NPBF MOSFET differ in several key parameters:

• Voltage rating: TIP120 (60V) higher than IRFZ44NPBF (55V).
• Current rating: IRFZ44NPBF (49A) much higher than TIP120 (5A).
• Gate threshold voltage: IRFZ44NPBF lower (2V) vs TIP120 (2.5V).
• Control signal: TIP120 requires base current (BJT), IRFZ44NPBF is voltage controlled (MOSFET).
• Heat dissipation: IRFZ44NPBF has lower on-resistance, dissipates less heat.

TIP120 is better for high-voltage switching with moderate current; IRFZ44NPBF suits high-current, low-voltage control with lower losses.