Axial inductors are measured in microhenries—and what that means for your circuit design

Inductors are the quiet workhorses behind many circuits. They hide in plain sight, shaping how signals rise and fall, how filters pass or reject certain frequencies, and how power flows smoothly in a design. If you’ve been staring at a schematic and wondering, “Which kind of inductor do people talk about when they say microhenry?”—you’re in the right place. The quick answer is: axial inductors. But there’s more to the story, and a few other forms to keep in mind as you build intuition.

What does inductance actually mean, and why microhenries?

Let’s start with a simple picture. Inductance, measured in henries (H), is a property that tells you how much magnetic field is produced per ampere of current and how much energy the coil can store in that field. In many real circuits, the numbers you care about aren’t big. They’re microhenries (µH), where 1 µH equals one millionth of a henry. In other words, these are tiny magnetic “tanks” tuned for quite specific, often high-frequency, applications.

A practical way to think about µH values is to imagine tiny bumps on a road. Each microhenry is a little impedance that helps or hinders signals as they travel. The smaller the inductance, the less it tends to slow down very fast signals; the larger the inductance, the more it can smooth or store energy in a slower, steadier way. So, when you’re working with high-speed digital or RF circuits, µH often comes up because it lines up with how those signals behave.

Axial inductors: the through-hole stalwarts

Axial inductors are the ones you’ll spot as a little cylindrical component with leads extending from both ends. They look almost like tiny resistors, but they house a coil that’s designed to produce inductance. The axial form factor makes them straightforward to handle in breadboards and through-hole PCBs, which is a big deal for hobbyists, prototypers, and many educational setups. Their shape isn’t just a cosmetic detail; it influences how much inductance you can pack into a given length and how comfortably they solder into a board.

Why are axial inductors so commonly discussed in the µH range? Because their size and construction are well suited to small inductance values. In many designs where space isn’t your biggest enemy and you want a predictable, easy-to-wire part, axial inductors deliver with modest inductance figures and reliable performance. You can grab a few µH values and drop them into your circuit without fuss, which makes them a natural reference point when you’re sorting through inductance concepts.

Other inductor families and where µH fits in

Inductors come in several flavors, and it’s helpful to know the contrasts:

• SMD inductors: Small, surface-mount inductors are the modern workhorses of many boards. They range widely in inductance, including the µH territory, and they’re built for compact layouts and automated assembly. If you’re moving from a breadboard to a compact PCB, you’ll likely encounter SMD inductors with values in the low µH to tens of µH range.

• Toroidal inductors: These bunsen-burner-shaped coils wrap around a doughnut-shaped core. They’re often chosen for their efficient magnetic path and compact footprint for the same or higher inductance values. They can deliver good Q factors in RF applications, where you want clean energy storage in a small space.

• Choke inductors: “Choke” is a term you’ll hear in power electronics. Chokes are meant to block AC while letting DC through, or to smooth ripple in a supply line. They can span a wide range of inductances, from small µH to millihenries (mH), depending on current demands and the application. The key idea is impedance at the frequency of interest, not just the numeric µH value alone.

Despite these differences, microhenry values can appear across all forms—SMD, toroidal, axial, and chokes—but the axial kind often shows up specifically when we’re talking about small, through-hole inductors where low µH values are practical and easy to source.

Measuring inductance: how µH gets verified

In practice, you don’t just eyeball the part and guess the value. Inductance measurement is a precise thing, especially when you’re designing a circuit that relies on a specific resonance or filter behavior. A common tool is an LCR meter (or an impedance analyzer). You connect the inductor, set the test frequency (often in the kilohertz to low-megahertz range for µH values), and the meter reports the inductance in microhenries alongside parasitic capacitance and resistance.

A few tips to keep measurements honest:

• Cold vs warm: inductors can shift a bit with temperature. If you’re chasing tight tolerances, measure in a temperature-controlled setting or note the temperature coefficient in your design notes.

• DC bias matters: some inductors change inductance as you apply a DC current (saturation and other core effects). If your circuit will carry DC, test with the expected bias in place.

• Frequency choice matters: at different test frequencies, the inductance reading can drift a little due to parasitics. For a first pass, measure at a frequency near where your circuit will actually operate.

Real-world cues: where µH axial inductors shine

You might wonder, “Who cares about these tiny µH figures in the real world?” The answer is: in many RF and high-speed signal paths, a few microhenries can dramatically shape the behavior of a network. A small inductor in a band-pass filter can define the center frequency, while in a matching network it helps tune impedance to get signals moving cleanly from one stage to the next.

In audio interfaces, you’ll find inductors in tone-control circuits and filtering stages where you want to preserve the signal’s character while suppressing unwanted frequencies. In RF front-ends, a µH-scale axial inductor can be part of the coil in a resonant circuit that tunes a receiver or transmitter to a precise frequency. And for general electronics hobbyists, axial inductors offer a friendly, tangible way to explore how inductance interacts with capacitance and resistance to shape a circuit’s response.

Choosing an inductor for a given µH target

When you’re selecting axial inductors (or any form) for a µH-valued job, a few criteria matter:

• Inductance and tolerance: ±5%, ±10% are common tolerances. If your circuit is sensitive to exact values (like a tuned RF network), you’ll want tighter tolerances.

• Saturation current and DC resistance (DCR): even a small inductor can heat up or saturate if you push too much current through it. Check the rated current and the DCR to ensure it fits your design’s power path.

• Core material: air-core inductors generally have lower losses and stable inductance over current, while ferrite or powdered iron cores can offer higher inductance in a compact form but may shift with temperature or current.

• Physical size and mounting: axial inductors are forgiving on a breadboard or perfboard, but if you’re moving toward a densely-packed PCB, you might switch to SMD types. Size also correlates with lead spacing, which matters for reliable soldering.

• Q factor and frequency response: in high-frequency applications, a higher Q (quality factor) means less energy lost as heat for a given inductance. If you’re building a finely-tuned circuit, this can be a deciding factor.

A mental model for quick decisions

Think of inductors as tiny energy storage devices for magnetic fields. Microhenry-scale inductors store a small amount of energy per cycle, enough to shape the signal without dominating the circuit’s behavior. Axial inductors, with their accessible form factor, are often your go-to when you’re working in the µH band and you want a straightforward, plug‑and‑play solution. If you need the part to fit a compact SMD footprint, you’ve got options in chip inductors that still carry microhenry values. If you’re optimizing for a compact RF stage, toroids or chokes become attractive for their magnetic efficiency and current handling.

A few quick analogies to keep things grounded

• Inductance is to alternating current what drag is to a bicycle ride: it resists rapid changes, smoothing the ride of the signal.

• A microhenry is like a small hill in the road. You can barely notice it at cruising speeds, but in certain frequencies, that hill changes how quickly you can accelerate and decelerate.

• Axial inductors are the reliable, familiar street bikes—easy to mount, easy to tune into a circuit, and perfectly adequate for lots of everyday rides.

Bringing it all together

To recap succinctly: when people talk about inductors in the microhenry range, axial inductors are a common, practical reference point. Their cylindrical, end-leaded design makes them a natural fit for through-hole boards and for designs where a modest inductance value is the goal. Other inductor forms—SMD, toroidal, and choke inductors—also cover µH territory, but axial inductors are especially associated with microhenry measurements because of their long-standing role in through-hole electronics and educational demonstrations.

If you’re building, experimenting, or just learning, here’s a simple way to keep the concepts clear:

• Identify the target inductance in µH for your circuit.

• Consider the operating frequency and whether DC bias will be present.

• Check tolerance, current rating, and temperature behavior.

• Pick the form factor that matches your board design (axial for through-hole convenience, SMD for compact PCBs, toroidal or choke for higher efficiency or specific applications).

A little extra food for thought

Inductors often don’t grab the spotlight the way a dramatic transformer or an elegant op-amp circuit does. Yet their influence is quiet but profound. They’re the reason a filter passes the right slice of a spectrum, or a power path remains stable under changing loads. So next time you run a hand through a parts drawer and spot a little axial coil, you’ll know there’s more to it than meets the eye—a tiny cylinder that tucks into a circuit and quietly helps the performance do its job.

If you’re curious to explore more, you can experiment with a few axial inductors of different µH values and watch how a simple LC filter behaves as you swap them. Listen for the way the resonance shifts, or feel how the impedance changes as you sweep frequency. It’s a small reminder that theory and hardware are not distant cousins but intimate relatives, working together to make electronics come alive.

Final thought

In the end, the world of inductors is a spectrum, and microhenries are a familiar anchor point for many practical designs. Axial inductors, with their approachable shape and reliable characteristics, give students and engineers a tangible way to connect theory with hands-on results. So when you’re mapping out a circuit and you see a microhenry target, you’ll know where to start—and you’ll have a clear sense of how axial inductors fit into the broader picture of inductive design.