Voltage Regulators
Linear regulators and references: dropout, stability requirements, quiescent current, and thermal limits.
Written and verified by John Merton · verified 2026-07-13
Voltage regulators turn one DC rail into another, and the category splits cleanly into linears and references. Linear regulators — the AMS1117 family, the LM1117, the TLV1117 — are for power: they burn the voltage difference as heat and pass current to a load. Voltage references — the REF3033 and its siblings — are for measurement: they supply a stable, accurate voltage to an ADC or DAC but cannot power anything more than a light resistive sense load.
The primary selection axis is dropout: the minimum voltage difference the regulator needs between input and output to stay in regulation. A reference with 1 mV of dropout at no load is a different animal from an LDO that needs 1.1 V of headroom at 800 mA. After dropout, the thermal budget dominates: power dissipated is (VIN − VOUT) × ILOAD, and a SOT-223 can shed more heat than a SOT-23. The parts in this category document both: the dropout voltage from the datasheet electrical table and the thermal resistance so you can do the junction-temperature arithmetic.
The gotchas that burn boards in this category are the ones the datasheet buries in the fine print: output capacitor ESR requirements that change with load, ground current that rises with dropout, and the difference between the headline 1 A rating and the real continuous rating at your ambient. Each part page covers its specific traps.
How to choose
The axes below are the criteria you actually weigh when selecting a part in this category.
- Dropout voltage at your actual load current
- The headline dropout is often spec'd at a fraction of the rated current. Check the dropout at the current your circuit actually draws.
- See:AMS1117-3.3LM1117-3.3TLV1117REF3033
- Thermal budget: (VIN - VOUT) × ILOAD vs package θJA
- Every volt of drop at every amp of load becomes heat in the package. Multiply, check θJA, and stay under the junction temperature limit at your worst-case ambient.
- See:AMS1117-3.3LM1117-3.3LM317T
- Output capacitor requirements
- LDOs often require a specific output capacitor ESR range for stability. Too much or too little ESR, and the regulator oscillates. References may need no capacitor at all — adding one can cause problems.
- See:AMS1117-3.3REF3033TLV1117
- Reference-grade accuracy vs LDO-grade accuracy
- A voltage reference like the REF3033 guarantees 0.2% initial accuracy and 75 ppm/°C drift. An LDO like the AMS1117 guarantees ±1.5% and drifts more. For ADC references, use a reference.
- See:REF3033AMS1117-3.3LM1117-3.3
Make the decision
Use the verified part pages for exact limits; use these tools to compare parts and test your operating point.
- Choosing a voltage regulator
Choose between a linear regulator, buck converter, boost converter, and voltage reference from the actual rail requirements.
- LDO vs buck for a 3.3 V rail
Compare headroom, linear heat, operating-point efficiency, noise, startup, and layout before choosing a step-down topology.
- AMS1117 vs LM1117 vs TLV1117
Compare exact manufacturer identities, dropout, ground current, capacitor rules, and the TLV1117 silicon-generation boundary.
- Linear-regulator thermal calculator
Estimate dissipation, junction rise, thermal margin, and dropout headroom from your board assumptions.
All parts in this category
- MC78055 V, 1 A fixed positive linear voltage regulator in TO-220 — onsemi's MC7800-series 78xx equivalent with internal current limiting, thermal shutdown, and safe-area compensation.Active
- AMS1117-3.31 A LDO with about 1.1 V dropout; ubiquitous 5 V to 3.3 V regulatorActive
- LM1117-3.3Fixed 3.3 V, 800 mA low-dropout regulator in the classic SOT-223 1117 footprint.Active
- REF3033Micropower 3.3 V precision series bandgap reference in SOT-23-3.Active
- TLV1117TI's 800 mA 1117-family linear regulator, adjustable and fixed, with two silicon generations shipping under one part numberActive
- LM317TTI's classic 1.5 A adjustable 3-terminal regulator in TO-220, the industry-standard LM317T — NRND, legacy-chip only, and emphatically not an LDONRND
- AP2112K-3.3TRG1Fixed 3.3 V CMOS LDO specified for at least 600 mA, with enable, ceramic stability, and output discharge.Status unverified
Compare specs
Parts in this guide verified against manufacturer datasheets; latest 2026-07-13.
| MPN | Package | Lifecycle | Headline spec |
|---|---|---|---|
| MC7805 | TO-220-3 (221AB) | Active | Output voltage (TJ = 25 degC): 5.0 V (min 4.8, max 5.2) |
| AMS1117-3.3 | SOT-223 | Active | Dropout at 0.8 A: 1.1 V typ / 1.3 V max at IOUT = 0.8 A (not specified at 1 A; Note 4: dropout is higher above 0.8 A) |
| LM1117-3.3 | SOT-223 (TI package code DCY), 6.50 × 3.50 mm body | Active | Output voltage (3.3 V fixed): 3.267 V min / 3.3 V typ / 3.333 V max (IOUT = 10 mA, VIN = 5 V, TJ = 25 C); 3.235 V min / 3.365 V max over the junction temperature range 0 C to 125 C (0 <= IOUT <= 800 mA, 4.75 V <= VIN <= 10 V) |
| REF3033 | SOT-23, 3-pin (TI package code DBZ) | Active | Output voltage / initial accuracy: VOUT 3.294 V min / 3.3 V typ / 3.306 V max; initial accuracy 0.2 % max (TA = 25C, VIN = 5V, ILOAD = 0mA) |
| TLV1117 | SOT-223, 4-pin (TI package code DCY) | Active | Input voltage range: 2.7 V min / 15 V max (TLV1117 adjustable); fixed versions: 2.9 V min (TLV1117-15), 3.2 V (TLV1117-18), 3.9 V (TLV1117-25), 4.7 V (TLV1117-33), 6.4 V (TLV1117-50), all 15 V max |
| LM317T | TO-220, 3-pin (TI package codes KCS, KCT) | NRND | Output voltage range: Adjustable: 1.25V to 37V |
| AP2112K-3.3TRG1 | SOT25 / SOT-23-5, 5-pin, tape-and-reel orderable | Status unverified | Output voltage and accuracy: 3.3 V fixed output; 3.251 V minimum, 3.3 V typical, 3.350 V maximum at VIN = 4.3 V and IOUT = 1 mA to 30 mA |
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