How to Make an LDO or Buck-Boost Converter

If you've ever searched for a 5V regulator circuit, chances are you've come across two very different solutions. One uses only a handful of components and can be assembled in minutes. The other looks far more intimidating, filled with inductors, capacitors, switching transistors and integrated circuits.

Both circuits regulate voltage, but they do so using completely different engineering principles.

This guide explains what components each regulator requires, how they work together and why one design is much simpler than the other.

THE TWO APPROACHES

LDO REGULATOR
- Removes excess voltage by converting it into heat.
- Very simple design.
- Few external components.
- Excellent for low-noise circuits.

BUCK-BOOST CONVERTER
- Converts electrical energy instead of wasting it.
- Much higher efficiency.
- More complex circuitry.
- Ideal for battery-powered electronics.

BUILDING AN LDO REGULATOR

MINIMUM COMPONENTS REQUIRED
- 1 × LDO Regulator IC
- 1 × Input Capacitor
- 1 × Output Capacitor
- Power Source
- Load

OPTIONAL COMPONENTS
- Reverse polarity protection diode
- Input fuse
- Ferrite bead for noise filtering
- TVS diode for surge protection
- LED power indicator
- Heat sink (for higher currents)

HOW THE CIRCUIT WORKS

Power Source
│
│
Input Capacitor
│
▼
LDO Regulator
│
Output Capacitor
│
▼
Load

The input capacitor smooths incoming voltage and helps absorb sudden current demands.

Inside the LDO is a precision voltage reference, an error amplifier and a pass transistor. The regulator constantly compares the output voltage against its internal reference.

If the output begins to fall, the pass transistor opens further to allow more current through.

If the output rises too high, the transistor closes slightly.

This adjustment happens thousands of times every second, keeping the output voltage remarkably stable.

The output capacitor smooths the regulator's response and prevents oscillations.

WHAT HAPPENS TO THE EXTRA VOLTAGE?

Example:

Input = 12V
Output = 5V
Current = 2A

The regulator simply burns off:

(12V - 5V) × 2A = 14 Watts

Those 14 watts become heat.

This is why larger LDOs often require heatsinks.

COMMON LDO ICs
- LM1117
- AMS1117
- MCP1700
- MCP1825
- TPS7A47
- LT3042
- XC6206

WHEN TO ADD A HEATSINK

Usually unnecessary when:
- Current is below 200mA.
- Voltage difference is small.

Recommended when:
- Current exceeds 500mA.
- Voltage drop exceeds several volts.
- Device becomes uncomfortable to touch.

BUILDING A BUCK-BOOST CONVERTER

MINIMUM COMPONENTS REQUIRED
- Buck-Boost Controller IC
- Power Inductor
- Input Capacitor
- Output Capacitor
- Switching MOSFET (internal or external)
- Schottky or synchronous rectifier MOSFET
- Feedback resistors
- Power Source
- Load

OPTIONAL COMPONENTS
- Soft-start capacitor
- Compensation network
- Current sense resistor
- EMI filter
- Input fuse
- TVS diode
- Thermal sensor

HOW THE CIRCUIT WORKS

Power Source
│
Input Capacitor
│
▼
Switching MOSFET
│
▼
Power Inductor
│
Rectifier / MOSFET
│
Output Capacitor
│
▼
Load

Unlike an LDO, the Buck-Boost converter never throws excess energy away.

Instead it repeatedly stores energy inside the magnetic field of the inductor.

When the switching transistor turns on, current builds inside the inductor.

When it switches off, the magnetic field collapses and pushes that stored energy toward the output.

By carefully controlling the switching time, the regulator can either reduce voltage, increase voltage or automatically perform both.

This entire process may happen anywhere from 100,000 to over 3 million times every second depending on the design.

WHY THE INDUCTOR IS ESSENTIAL

The inductor is the heart of every switching regulator.

Without it:
- Energy cannot be temporarily stored.
- Voltage cannot be increased.
- Efficient conversion becomes impossible.

Think of the inductor as a rechargeable magnetic battery that charges and discharges millions of times every second.

WHY THE CAPACITORS ARE NEEDED

INPUT CAPACITOR
- Reduces voltage spikes.
- Supplies sudden bursts of current.
- Reduces input ripple.

OUTPUT CAPACITOR
- Smooths switching pulses.
- Produces stable DC voltage.
- Reduces output ripple.

WHY FEEDBACK RESISTORS ARE REQUIRED

Buck-Boost regulators continuously measure their own output.

A resistor divider sends a tiny sample of the output voltage back to the controller.

The controller compares this sample with its internal voltage reference.

If the output is too low:
- Switching duty cycle increases.

If the output is too high:
- Switching duty cycle decreases.

This closed-loop feedback system is what allows modern converters to maintain stable voltage despite changing loads.

COMMON BUCK-BOOST CONTROLLER ICs
- TPS63060
- LTC3531
- LTC3115
- XL6009
- LM5175
- MP3429
- TPS63802

CHOOSING THE RIGHT INDUCTOR

Important specifications include:
- Inductance (µH)
- Saturation current
- DC resistance (DCR)
- Core material
- Switching frequency compatibility

Choosing the wrong inductor can reduce efficiency or prevent the regulator from functioning correctly.

CHOOSING THE RIGHT CAPACITORS

Ceramic capacitors are preferred because they:
- Have low ESR.
- Handle high-frequency switching well.
- Improve efficiency.
- Reduce ripple.

Electrolytic capacitors are still used where larger capacitance is needed but usually have higher ESR.

PCB LAYOUT MATTERS

For LDOs:
- PCB layout is generally forgiving.
- Keep capacitors close to the regulator.
- Use a solid ground plane when possible.

For Buck-Boost converters:
- PCB layout is critical.
- High-current loops should be as short as possible.
- Place the input capacitor close to the switching MOSFET.
- Keep the inductor near the controller.
- Separate noisy switching nodes from sensitive analog signals.
- A poor layout can increase heat, ripple and electromagnetic interference even if the schematic is correct.

BUILD DIFFICULTY COMPARISON

LDO
- Components: Very few
- Design complexity: Low
- PCB layout: Simple
- Heat management: Often required
- Efficiency: Moderate to low

Buck-Boost
- Components: Many more
- Design complexity: High
- PCB layout: Critical
- Heat management: Usually minimal
- Efficiency: Very high

WHEN SHOULD YOU BUILD AN LDO?
- Audio circuits.
- Sensor interfaces.
- Low-current electronics.
- Analog instrumentation.
- Projects where simplicity is more important than efficiency.

WHEN SHOULD YOU BUILD A BUCK-BOOST CONVERTER?
- Battery-powered devices.
- USB-C projects.
- Portable electronics.
- Solar-powered systems.
- Robotics.
- Embedded computers.
- High-current applications.
- Any design where efficiency is important.

Building an LDO is straightforward because most of the regulation circuitry is integrated into a single chip and only a few external components are required.
- Building a Buck-Boost converter is more involved because energy must be switched, stored, monitored and filtered continuously using several supporting components.
- An LDO trades efficiency for simplicity and exceptionally clean output.
- A Buck-Boost converter trades simplicity for efficiency and flexibility.
- Neither design is universally better. Engineers choose the one that best fits the application's voltage range, power requirements, noise tolerance and available space.