Recommended Free Tools
An analog active load can draw a set current from a power supply while its output voltage changes. The simplest version is a feedback-controlled current sink: an op amp adjusts a power MOSFET until the voltage across a current-sense resistor matches an adjustable reference. It is useful for steady-state testing, but the MOSFET turns the source’s output power into heat, so safe operation depends on the transistor’s linear-mode safe operating area (SOA) and the complete cooling path—not its headline wattage alone.
How an analog active load holds current steady
Connect the device under test (DUT) to a low-side current sink containing a power MOSFET and a known sense resistor. The DUT supplies current through the MOSFET; the resistor develops a voltage proportional to that current. An op amp compares this voltage with a setpoint and adjusts the MOSFET gate. If the measured voltage falls below the setpoint, the op amp drives the MOSFET to conduct more; if it rises above the setpoint, it reduces conduction. This is negative feedback.
In the idealized circuit, the relationship is I ≈ Vset / Rsense. For example, with a 0.1 Ω shunt, a 0.1 V setpoint corresponds ideally to 1 A, and 1 V corresponds to 10 A. Those are circuit relationships, not a guarantee that a particular build can safely reach those currents. The op amp supplies gate control; the MOSFET provides the current-handling capability, while the sense resistor helps stabilize the loop. See Analog Devices’ explanation of electronic-load feedback and its current-sink example and op-amp considerations.
What the referenced project used—and what its ratings mean
Hackster’s project overview lists an IRFP250 MOSFET, LM358 op amp, 100 nF capacitor, 20 kΩ trimmer, 0.1 Ω 10 W shunt resistor, 1 kΩ resistor, PCB, heatsink and 12 V fan. This is the parts list reported for that project, not a universal design recipe or an independently validated bill of materials. Consult the Hackster project overview for its description.
Windows Errors? Fix Them Before They Spread
Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallOutdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware match#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
The same overview reports a 0–10 A adjustment range, 120 W maximum power, 200 V maximum voltage and dissipation up to 190 W. These are project-reported claims; the available description does not establish that the maxima can be used simultaneously or that they apply to a recreation with different components, layout, cooling or ambient temperature. Treat them as reported specifications, not as a safe operating envelope. The relevant operating point must be checked against the chosen transistor’s SOA and thermal limits.
Check the design before applying power
Verify MOSFET linear-mode safe operating area
An active load usually operates its MOSFET in its linear region, where the device drops voltage while carrying current. Check the selected part’s SOA for the actual drain current, drain-source voltage, mounting temperature and duration of the load. A transistor’s headline power rating alone does not show that it can safely dissipate a given amount in linear operation. Exceeding the relevant SOA can cause failure. Analog Devices discusses these limits in Part 2 of its electronic-load design guidance.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
Calculate the full thermal path
Estimate junction temperature from the heat generated and the thermal resistance from junction to case and from case through the mounting interface and heatsink to ambient. Include the effects of mounting and airflow. The MOSFET junction temperature must remain within the device’s rating; a package’s outer surface does not directly reveal junction temperature. The load’s dissipated power is approximately DUT voltage multiplied by load current, with additional heat in the shunt and other components. Fan cooling can help, but it does not replace the calculation.
Size the shunt for heat and measurement quality
The sense resistor dissipates P = I²R. With a 0.1 Ω shunt, for example, 10 A would mean 10 W dissipated in the resistor under ideal steady-state conditions. Choose a resistor with an appropriate power rating and account for precision and resistance change with temperature. A nominal 10 W rating should not be treated as permission to run continuously at that dissipation without checking the component’s conditions and thermal environment.
The Tool Desk
Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Rank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
Choose an op amp that fits the actual circuit
Check supply-voltage range, input common-mode range, output swing and loop stability in the circuit as built. In a low-side arrangement, the sense voltage may be close to ground; not every op amp can measure that voltage or drive the MOSFET gate appropriately from the available supply. Analog Devices’ AN-105 notes the need for a suitable single-supply or rail-to-rail type in relevant near-ground configurations. Do not assume that op amps with similar names or pinouts are interchangeable.
Keep the sense path and wiring appropriate to the test
For steady-state tests, safe current handling and thermal design are usually more important than fast response. If you need to measure rapid current changes, shunt parasitic inductance and layout can distort the sensed voltage and slow the current rise. Low-inductance construction and careful sense routing matter more in that case. At high current, wiring resistance and inductance can also affect the result, particularly with low-voltage supplies; keep the current path and sense connections appropriate to the intended measurement.
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
Active sink or fixed power resistor?
| Consideration | Fixed power resistor | Analog active sink |
|---|---|---|
| Current as DUT voltage changes | Changes with voltage according to the resistor value. | Feedback adjusts MOSFET conduction to maintain the setpoint, within the circuit’s operating limits. |
| Adjustability | Requires changing the resistor or using a resistor network. | Setpoint can be adjusted by changing the reference voltage. |
| Heat distribution | Most load heat is dissipated in the power resistor. | The MOSFET dissipates substantial heat; the shunt also heats up. |
| Circuit complexity | Simple to implement. | Needs a feedback circuit, suitable MOSFET and op amp, sensing, and thermal design. |
| Transient testing | Does not actively change its draw. | Can support controlled current changes, but actual response depends on the loop and layout. |
Use a resistor when a simple, fixed load is sufficient and its current variation with DUT voltage is acceptable. An active sink is useful when you need a chosen current across a changing output voltage or controlled changes in load current. Neither approach removes the need to keep components and wiring within their ratings.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Set up the test safely
- Define the test point. Record the DUT voltage and intended current, then calculate the approximate MOSFET dissipation as voltage multiplied by current and the shunt dissipation as current squared multiplied by resistance.
- Check component limits. Confirm the MOSFET SOA at the operating voltage, current and test duration; verify the thermal path; and check the shunt and op amp ratings for the circuit.
- Prepare the current path. Use wiring and connectors suitable for the intended current, and make sense connections that do not inadvertently include unwanted wiring drops in the measurement.
- Monitor operation. Observe current and temperature during the test. Stop if the current becomes unstable or temperatures approach component limits.
- Use added caution at high voltage. The load does not make the DUT safe to touch. High-voltage testing presents a serious shock hazard; Analog Devices’ active-load overview explains the use case and thermal considerations.
When comparing MOSFET candidates, compare linear-mode SOA at the actual operating point, thermal resistance, voltage and current limits, mounting needs and availability. The cited material does not establish a tested winner among alternative parts.
Do these 3 things before closing this tab:
1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsQuick Recap
Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
