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Q: What's the biggest difference between 78D05 and 78L05?

Output current - 1A versus 100mA, a 10x gap. Everything else (5V output, 78xx dropout, PSRR) is family-familiar. The current class decides the die, the package, and the thermal budget.

Q: Can I swap 78L05G and 78D05AL in the same footprint?

No - different packages and mirrored pins. SOT-89 runs O-G-I (OUT on pin 1); TO-252 runs I-G-O (IN on pin 1). The footprints are physically incompatible, and forcing either one feeds the input into the output pin.

Q: Where does the 78M05 fit between them?

500mA - the middle child, also in TO-252 with I-G-O pins. If your rail sits between 100mA and 500mA, the 78M05 class is the right die; the 78D05AL still works there, just with more headroom than you need.

Q: Why would I use the tiny one at all if the big one works?

Quiescent current, footprint, and honesty about the load. The 78L05G draws 2mA idle versus 8mA, sits in a third of the space, and matches a 20mA bias rail without the oversized-regulator waste the forums keep warning about.

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78D05AL-TN3-R vs 78L05G-AB3-R — Full Comparison & Selection Guide

2026/8/19 14:42:58

78D05AL-TN3-R vs 78L05G-AB3-R — Full Comparison & Selection Guide | ICMASS

The difference in one line: 78D05AL-TN3-R is the 1A main-rail regulator in a TO-252; 78L05G-AB3-R is the 100mA bias-rail regulator in a SOT-89. Ten times the current, twenty-eight times the dissipation budget, and a mirrored pinout between them.

Pick the 78D05AL when the 5V rail feeds the logic, the relays, or the sensors; pick the 78L05G when the 5V rail feeds an op-amp bias, a reference, or an MCU that draws tens of milliamps.

In the boards we see at distribution (2025–2026), the failure pattern is usually not the current rating — it's the footprint: the two parts carry mirrored pin orders, and a layout that assumes either one silently feeds the input into the output pin.

78D05AL-TN3-R vs 78L05G-AB3-R: Side-by-Side Comparison

Parameter	78D05AL-TN3-R	78L05G-AB3-R
Manufacturer	UTC (Unisonic)	UTC (Unisonic)
Type	Fixed linear regulator	Fixed linear regulator
Output Voltage	5V fixed	5V fixed
Output Current	1A (A-suffix class)	100mA (L class)
Package	TO-252 (DPAK)	SOT-89
Pinout	I-G-O (1=IN, 2=GND, 3=OUT)	O-G-I (1=OUT, 2=GND, 3=IN)
Maximum Input Voltage	35V	30V
Dropout Voltage	2V @ 500mA	1.7V max @ 40mA
Quiescent Current	8mA	2mA (5.5mA max)
PSRR @ 120Hz	80dB	80dB
Output Noise	40µV	40µV
Power Dissipation	10W (with copper)	350mW (SOT-89)
Operating Temperature	-40°C to +85°C	-40°C to +85°C
Max load @ 12V in	~700mA (7W budget)	~50mA (350mW budget)
Max load @ 30V in	~200mA (5W budget)	~14mA
Best For	Main rails, logic, relays	Bias rails, references, small MCUs

The whole comparison in one row: at 12V in, the 78D05AL delivers about fourteen times the load current of the 78L05G before either hits its thermal limit — but the 78L05G draws a quarter of the quiescent current and sits in a third of the footprint.

Output current class (mA) — the 10x gap between them

78L05G (SOT-89)

100

78M05 (TO-252)

500

78D05AL (TO-252)

1000

The 78L05G exists because most bias rails never exceed 100mA — sizing the main-rail part for a bias rail just wastes board space and burns extra quiescent current.

This mirror is the #1 field failure with the 78 family. A board laid out for one part gets a rework with the other, the input lands on the output pin, and the regulator lets the smoke out on power-up. The silk screen can't save you — only the datasheet can.

Key Differences

Current class — 1A vs 100mA

Ten times the output current, and ten times the die. The 78D05AL is a 1A-class regulator; the 78L05G is 100mA. Both regulate 5V, but the 78L05G at 80mA of load is already near its limit, while the 78D05AL at 80mA is barely breathing.

The thermal envelope — 10W vs 350mW

Twenty-eight times the dissipation budget, and it all comes down to the board. The TO-252 pours heat through its GND tab into the copper pour; the SOT-89 has a third of the metal. At 12V in, that's ~700mA of headroom for the 78D05AL versus ~50mA for the 78L05G.

Package dissipation budget (mW) — the 28x thermal gap

78L05G (SOT-89)

350

78D05AL (TO-252)

10,000

At 12V in, that's ~50mA of safe load for the SOT-89 versus ~700mA for the TO-252 — the current-class gap and the thermal gap are really the same story.

Quiescent current — 2mA vs 8mA

The bias rail wins on idle draw. On a rail that mostly sleeps, the 78L05G's 2mA beats the 78D05AL's 8mA four times over — which is why the small part keeps earning its place next to the big one on the same board.

Mirrored pinout — O-G-I vs I-G-O

Same three functions, opposite order. SOT-89 puts OUT on pin 1; TO-252 puts IN on pin 1. The tab connection differs too: GND on the TO-252, unconnected on the SOT-89. A drop-in swap without a footprint review is a short circuit waiting to happen.

When to Choose 78D05AL-TN3-R / When to Choose 78L05G-AB3-R

✅ Choose 78D05AL-TN3-R when:

The rail drives logic, relays, or sensors. Anything that draws hundreds of milliamps belongs on the 1A part.
12V or 24V input with a real load. 35V input and 10W of budget handle the transients and the current.
You need the GND tab for thermal design. The TO-252 pours onto the ground plane — the board becomes the heatsink.
Automated SMD assembly with standard packages. TO-252 is a mainstream pick-and-place body.

✅ Choose 78L05G-AB3-R when:

The rail is a bias supply under 100mA. Op-amp rails, references, pull-up domains — the L class exists for exactly these.
Board space is tight. SOT-89 is a third of the TO-252 footprint.
Idle draw matters. 2mA quiescent on a mostly-sleeping rail beats 8mA.
You need a tiny 5V next to a main rail. The classic pairing: 78D05AL for the logic, 78L05G for the bias, one BOM, two packages.

Frequently Asked Questions About 78D05 vs 78L05

Q1: What's the biggest difference between 78D05 and 78L05?

A: Output current — 1A versus 100mA, a 10x gap. Everything else (5V output, 78xx dropout, PSRR) is family-familiar. The current class decides the die, the package, and the thermal budget.

Q2: Can I swap 78L05G and 78D05AL in the same footprint?

A: No — different packages and mirrored pins. SOT-89 runs O-G-I (OUT on pin 1); TO-252 runs I-G-O (IN on pin 1). The footprints are physically incompatible, and forcing either one feeds the input into the output pin.

Q3: Where does the 78M05 fit between them?

A: 500mA — the middle child, also in TO-252 with I-G-O pins. If your rail sits between 100mA and 500mA, the 78M05 class is the right die; the 78D05AL still works there, just with more headroom than you need.

Q4: Which one has lower dropout?

A: At low current, the 78L05G: 1.7V max at 40mA versus 2V at 500mA. Both are classic 78xx numbers — neither is low-dropout. Below about 6V of input, neither part can guarantee a clean 5V.

Q5: How much load can each handle from a 12V input?

A: The 78D05AL manages roughly 700mA before the 7W dissipation is too much; the 78L05G tops out around 50mA. The gap is the thermal envelope: 10W of TO-252 budget versus 350mW of SOT-89 budget, both burning (12V − 5V) per amp.

Q6: Why would I use the tiny one at all if the big one works?

A: Quiescent current, footprint, and honesty about the load. The 78L05G draws 2mA idle versus 8mA, sits in a third of the space, and matches a 20mA bias rail without the oversized-regulator waste the forums keep warning about.

Q7: Are the tabs the same?

A: No — the TO-252 tab is GND and carries the heat into the copper; the SOT-89 tab is a mechanical pad. Layout the TO-252 tab onto the ground pour with thermal vias; treat the SOT-89 tab as solder attachment, not a heatsink.

Q8: How much do they cost and are they in stock?

A: Volume pricing typically ranges from $0.03–$0.12/unit depending on part and quantity. ICMASS stocks both in Shenzhen and ships same-day. Contact us for a quote on your specific mix.