Regulator Compare

Set the input voltage, desired output voltage, load current, and switching efficiency — the widget instantly calculates the power loss and efficiency for both a linear (LDO) and a switching regulator. See exactly when a heatsink becomes mandatory and how much energy you save by switching.

V_in: 12 VV_out: 5 VI_out: 1 Aη_switching: 88 %

Linear

\eta = \frac{V_{out}}{V_{in}} = \frac{5}{12} = 41.7\%

P_{loss} = (V_{in} - V_{out}) \times I_{out} = 7.00\;\text{W}

Switching

P_{in} = \frac{V_{out} \times I_{out}}{\eta_{sw}} = 5.68\;\text{W}

P_{loss} = P_{in} - P_{out} = 0.68\;\text{W}

Linear Efficiency

41.7%

Switching Efficiency

88%

Heatsink recommended: Linear regulator dissipates 7.00 W (> 1 W).

Quick experiments

12 V → 5 V at 1 A. The linear regulator burns 7 W — enough to need a heatsink. The switcher at 88% loses only 0.68 W.
Push the dropout. Set V_in just above V_out — linear efficiency climbs, but the dropout warning fires when the margin is too thin.
High current. Raise I_out to 3 A and watch the linear loss bar skyrocket while the switching loss grows proportionally.

Voltage regulator types

A voltage regulator maintains a stable DC output despite variations in input voltage and load current. The choice between linear and switching regulators is primarily a trade-off between simplicity/noise and efficiency.

Linear regulator (LDO)

Drops excess voltage across a pass transistor: P_loss = (V_in − V_out) × I_load. Simple, very low noise, but efficiency falls sharply when V_in ≫ V_out. Use when efficiency is secondary and clean output is required (ADC supplies, RF circuits).

Switching regulator (buck/boost)

Buck (step-down): V_out = D × V_in, where D = duty cycle. Efficiency 85–95 %.
Boost (step-up): V_out = V_in / (1−D). Raises voltage, reduces current.
Switching regulators introduce ripple and EMI — output filter (LC) essential.

Learn more → Linear vs Switching Regulators — Learn

Formula reference

Linear regulator dissipation: $P_{diss} = (V_{in} - V_{out}) \, I_{load}$
12 V to 5 V at 1 A wastes 7 W as heat.
Linear regulator efficiency: $\eta = \dfrac{V_{out}}{V_{in}}$
Set purely by the voltage ratio — the load current cancels.
Dropout condition: $V_{in} \ge V_{out} + V_{dropout}$
A 7805 needs about 2 V; an LDO needs a few hundred millivolts.
Junction temperature: $T_j = T_a + P_{diss} \, R_{\theta JA}$
Check against the maximum rating before trusting a design.

Symbol	Meaning	Unit
$V_{dropout}$	Minimum input-to-output difference	V
$R_{\theta JA}$	Junction-to-ambient thermal resistance	°C/W
$T_j$	Junction temperature	°C

Common mistakes

Choosing a linear regulator for a large voltage drop.
Dissipation is the voltage difference times current. Dropping 24 V to 5 V at 1 A burns 19 W — use a switcher.
Ignoring dropout voltage.
A 7805 cannot make 5 V from a 6 V battery. Once the input sags into dropout, the output simply follows it down.
Omitting the input and output capacitors.
Most regulators need specific capacitance for stability. Leaving them out, or using the wrong ESR, makes the regulator oscillate.
Sizing the heatsink from ambient rather than junction temperature.
Work from junction = ambient + dissipation × thermal resistance. A part that feels warm can still be over its junction rating internally.
Assuming a switcher is always the better choice.
Switchers inject ripple at their switching frequency. For analogue, RF and audio rails a linear regulator's quiet output is worth the lost efficiency.

Frequently asked questions

What is the difference between a linear regulator and a switching regulator?

A linear regulator burns the excess voltage as heat, so efficiency is roughly output divided by input voltage. A switching regulator chops and filters the input, reaching 85 to 95 percent efficiency regardless of the voltage difference.

How much heat does a linear regulator produce?

Dissipation is the input minus output voltage, times the load current. Dropping 12 V to 5 V at 1 A wastes 7 W as heat, which needs a substantial heatsink.

What is dropout voltage?

The minimum input-to-output difference a linear regulator needs to keep regulating. A 7805 typically needs about 2 V, so it cannot produce 5 V from a 6 V supply. Low-dropout regulators manage a few hundred millivolts.

When should I choose a linear regulator over a switcher?

Choose linear when the voltage difference and current are both small, or when noise matters — analogue front ends, RF and audio. Linear regulators produce no switching ripple and need far fewer external parts.

Why does my switching regulator produce noisy output?

Switching regulators generate ripple at their switching frequency, worsened by poor layout. Keep the high-current loop small, use low-ESR capacitors, and add an LC filter or a small LDO downstream where clean rails are needed.