M9OMS VLDO V2
A discrete very low dropout (VLDO) linear voltage regulator for QRP radios. Selectable 9.0 V / 12.0 V / 13.8 V at up to 2 A.
Where to buy
- M9OMS eBay store — all current and previous designs.
V2 at a glance
| Type | Discrete low-dropout (LDO) linear regulator |
| Output | 9.0 V / 12.0 V / 13.8 V (jumper-selectable, trimmed via R7) |
| Max current | 2.0 A continuous |
| Dropout | < 100 mV (regulation threshold) at 1 A |
| Switching noise | None — linear topology |
| Designed for | QRP radios and other portable HF rigs |
Why a discrete LDO?
Modern QRP rigs need a stable rail, but hobbyist switching modules can introduce noise. Many ‘ready’ LDO boards need too much headroom to hold regulation as a battery discharges. The VLDO V2 stays quiet, keeps regulating close to the input voltage, and is built for rapid RX-TX current changes.
Documentation
- Design rationale, schematic lineage & full specification table — the complete project README.
- Oscilloscope measurements — oscilloscope captures of 0.1 A ↔ 1.5 A load steps at the 12 V setting.
- Static DC measurements — hardware-verified DC and thermal data (KC7XE, June 2026).
- V1.1 vs V2 comparison — like-for-like bench comparison of dropout and load regulation.
Credits
V2 design and hardware by M9OMS. DC evaluation by KC7XE. Stability evaluation by CR7BTQ.