Introduction
In the world of electronics, MOSFETs are essential components for switching and amplification tasks. Among these, the FDS6910 stands out as a dual N-channel MOSFET packaged in a single chip, designed to offer low on-resistance and high-speed switching in a compact form factor. This project explores how to build a compact, high-speed dual switch circuit using the FDS6910 to control two separate loads efficiently with minimal power loss.Instead of a generic or comprehensive guide to MOSFET usage, this article focuses specifically on the design and construction of a dual high-speed load switch. This device can be used in battery-powered applications, portable gadgets, or wherever efficient power control for two loads is required.
Why Use the FDS6910?
The FDS6910 is a dual N-channel MOSFET housed in a small SOT-23 package. Its key features include:● Very low on-resistance (R_DS(on)), leading to minimal voltage drop and heat generation
● Dual MOSFETs in a single package, simplifying layout and reducing component count
● Fast switching speeds suitable for power management tasks
● Compact size, perfect for space-constrained projects
Because of these properties, the FDS6910 is ideal for building a dual switch where two separate loads can be powered or disconnected efficiently without bulky or complicated circuitry.
Project Overview
Objective
The goal is to create a dual high-speed switch module that can independently control two loads from a single power source. This module can be powered by a DC battery or regulated power supply and controlled via simple mechanical switches or logic signals (e.g., from an Arduino or microcontroller, but this project does not require any code).Applications
● Battery-powered LED lighting systems, enabling independent control of two light strings● Switching power to two sensors or modules in an IoT device
● Power control for small motors or actuators in robotics
● General-purpose dual channel power management in embedded projects
Components Required
● FDS6910 dual N-channel MOSFET (1 piece)● 2 Mechanical toggle switches or pushbuttons (for manual control)
● 2 Load devices (e.g., LED arrays, small motors, or sensor modules)
● DC power supply or battery pack (5-12V recommended)
● Resistors (2 x 10kΩ for pull-down on MOSFET gates)
● Perfboard or PCB for assembly
● Connecting wires and soldering tools
● Enclosure box (optional)
Design Explanation
How the FDS6910 Controls Loads
The FDS6910 contains two N-channel MOSFETs sharing a common source ground. Each MOSFET's gate can be driven high (to the supply voltage level) to turn the corresponding MOSFET on, allowing current to flow from the drain to the source — effectively powering the load connected to the drain.Because the FDS6910 has very low on-resistance, the power loss during conduction is minimal, which keeps the device cool even when handling currents up to a few amperes. This makes it excellent for battery-powered applications where efficiency matters.
Manual Control Circuit
To keep things simple and without any microcontroller or code, manual toggle switches or pushbuttons are used to apply the gate voltage. When a switch is closed, it connects the gate to the positive supply voltage, turning the MOSFET on and powering the load. When the switch is open, a pull-down resistor ensures the gate is held at ground potential, turning the MOSFET off and disconnecting the load.Step-by-Step Assembly
1. Preparing the Circuit Board
Start by laying out the components on a perfboard. The FDS6910 has six pins: two gates, two drains, and two sources (common ground). Plan the layout so that the MOSFET sits centrally, with the two gates accessible for switches, and the drains routed toward load connectors.2. Wiring the Power and Loads
● Connect the negative terminal of the power supply to the MOSFET sources and the common ground line.● Connect the positive terminal of the power supply to the positive side of each load.
● Connect each load's negative terminal to the drain of each MOSFET.
3. Gate Control
● Attach a toggle switch or pushbutton for each MOSFET gate.● Connect one side of the switch to the positive voltage supply.
● Connect the other side of the switch to the corresponding MOSFET gate pin.
● Place a 10kΩ resistor between each gate and ground to ensure the MOSFET remains off when the switch is open.
4. Final Assembly
Solder all components carefully, check for shorts, and mount the load devices. If desired, place the whole assembly inside an enclosure for protection.Testing the Dual Switch Module
Once assembled, connect the power source and loads. Flip the first switch; the first load should power on immediately without noticeable delay. Flip the second switch independently to power the second load. Both loads can be controlled independently without interference.Measure the voltage across the loads and MOSFETs under load to verify minimal voltage drop, indicating efficient switching.
Practical Observations and Improvements
Heat and Efficiency
During prolonged operation, the FDS6910 remains cool due to its low on-resistance. For loads under 2A, no additional heat sinking is required. For higher currents, adding a small heatsink or placing the MOSFET on a larger copper area on the PCB will help dissipate heat.Expanding Control Methods
Though this project uses manual switches, the gate inputs can be driven by any digital logic device, including microcontrollers, sensors, or remote switches. This opens possibilities for automation and integration into smart systems.Modular Design
This compact dual switch module can be used standalone or combined with other modules. For example, you could connect multiple units in parallel or cascade them to control multiple devices efficiently.Real-World Use Case: Portable LED Lighting System
To demonstrate a practical application, the dual switch module was used to control two separate LED strips on a portable camping lantern.● The first load consisted of a white LED strip for bright illumination.
● The second load was a red LED strip used for night vision preservation.
Using the FDS6910 module, the camper could independently switch between white and red lighting without any noticeable power loss or heat buildup. The low-voltage drop ensured longer battery runtime, essential for extended camping trips.
Conclusion
This project showcases how the FDS6910 MOSFET can be harnessed to create a simple yet highly effective dual load switch. By focusing on hardware-only manual control, the build remains accessible for hobbyists without coding skills, emphasizing practical hands-on skills in electronics.The compact size, low power loss, and ease of integration make this dual switch module an excellent building block for many DIY electronics projects, especially those involving power management in battery-powered devices.
This specific, focused project highlights the importance of selecting the right MOSFET and designing a straightforward circuit that meets real-world needs with minimal complexity.
BR 21246 
US 19587 
GB 12706 
CA 9911 
AU 8177 
IE 5247 
VN 4167 
IN 3677 
