Infineon BUZ31 Power MOSFET: Datasheet, Pinout, and Application Circuits
The Infineon BUZ31 is a classic N-channel power MOSFET that has established itself as a reliable workhorse in the world of power electronics. Renowned for its robustness and high switching speed, this device is designed for a variety of medium-power applications, from switch-mode power supplies (SMPS) to motor control and audio amplifiers.
This article provides a detailed overview of the BUZ31, covering its key specifications from the datasheet, its pinout configuration, and common application circuits.
Datasheet Overview and Key Specifications
The BUZ31 is characterized by its high efficiency and fast switching capabilities. Key absolute maximum ratings and electrical characteristics from its datasheet include:
Drain-Source Voltage (VDS): 100 V. This defines the maximum voltage the MOSFET can block when turned off.
Continuous Drain Current (ID): 3.5 A at a case temperature (TC) of 25°C. This is the maximum continuous current it can conduct.
Pulsed Drain Current (IDM): 14 A. The device can handle much higher peak currents for short durations.
On-Resistance (RDS(on)): 0.1 Ω (max) at ID = 2.5 A, VGS = 10 V. A low on-resistance is crucial for minimizing conduction losses and improving efficiency.
Gate-Source Voltage (VGS): ±20 V. The gate is sensitive and must be driven with a voltage within this range; typically, 10V is used for full enhancement.
Total Power Dissipation (Ptot): 75 W (with an infinite heat sink). In practice, a heatsink is almost always required to approach this value.
Pinout Configuration
The BUZ31 is most commonly available in the TO-220 package, a through-hole package designed for easy mounting to a heatsink. The pinout is standard for many TO-220 MOSFETs:
Pin 1 (Gate): This is the control pin. A voltage applied between the Gate and Source controls the flow of current between the Drain and Source.
Pin 2 (Drain): The main load current enters through this pin. It is connected to the metal tab, which is also electrically the Drain pin. This must be considered for isolation when mounting the heatsink.
Pin 3 (Source): The main load current exits through this pin. This is typically the ground reference for the gate drive signal.
Application Circuits
1. Low-Side Switch Circuit
This is one of the most common applications. The BUZ31 is placed between the load and ground (GND). A driver circuit (like a microcontroller GPIO pin) is connected to the Gate through a series resistor (e.g., 10Ω to 100Ω) to dampen oscillations. The load (e.g., a DC motor, relay, or lamp) is connected between the positive supply rail and the Drain pin. When a voltage greater than the threshold (typically 2-4V) is applied to the Gate, the MOSFET turns on, completing the circuit and powering the load.
2. Simple Switch-Mode Power Supply (SMPS)
The BUZ31 is well-suited for use as the main switching element in flyback or forward converter SMPS designs. In such a circuit, the MOSFET is driven by a dedicated PWM controller IC. It rapidly switches on and off to control the energy transfer from the primary side of a transformer to the secondary, isolated output side. Its fast switching speed is critical for the efficiency and high-frequency operation of these power supplies.
3. Linear Audio Amplifier Output Stage
In Class AB amplifier designs, the BUZ31 can be used in the output stage to source current to the loudspeaker. While not as common as bipolar transistors in modern designs, power MOSFETs like the BUZ31 offer a simpler drive requirement and can provide excellent audio fidelity.
Important Design Considerations
Gate Driving: While the gate is essentially a capacitor, a driver IC is recommended for fast switching to quickly charge and discharge the gate, minimizing switching losses.
Heatsinking: Due to power dissipation (P = I2 RDS(on)), a proper heatsink is mandatory for any significant current. The tab is electrically live (Drain), so an insulating kit (mica washer, silicone pad) must be used if the heatsink is grounded.
Protection: Incorporate a flyback diode for inductive loads (like motors) to protect the MOSFET from voltage spikes generated when the current is suddenly interrupted.
ICGOOODFIND: The Infineon BUZ31 remains a versatile and robust N-channel power MOSFET, ideal for designers working on medium-power switching applications up to 100V and 3.5A. Its strengths lie in its low on-resistance, high switching speed, and durable TO-220 package. When implementing it, careful attention to gate driving, heatsinking, and protection circuits is essential for reliable and efficient performance.
Keywords: Power MOSFET, Switching Circuit, Datasheet, TO-220, On-Resistance
