BAR46A - Small Signal Schottky Diode SOT-23 | STMicroelectronics
MPN: BAR46A β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.08 | $0.08 |
| 10 | $0.06 | $0.60 |
| 100 | $0.04 | $4.00 |
| 500 | $0.03 | $15.00 |
| 1,000 | $0.025 | $25.00 |
BAR46A Overview
A small signal Schottky diode is a metal-semiconductor junction rectifier that replaces the conventional P-N junction with a Schottky barrier, eliminating reverse-recovery charge. Within the power-discrete hierarchy it sits at the diode -> rectifier -> Schottky rectifier -> discrete semiconductor level, and it is commonly used wherever a low forward voltage drop and negligible switching losses matter more than ultra-high blocking voltage.
Per the STMicroelectronics datasheet, the BAR46A's key benefits are very small conduction losses, negligible switching losses, and a low forward voltage drop in a compact surface-mount device (SMD). Because there is no reverse recovery, switching power loss is essentially zero, which makes the part attractive in switching and line-protection circuits operating at moderate currents. The high reverse-voltage rating differentiates the A version from the standard BAR46 in the same family.
The BAR46A architecture uses a high-barrier Schottky metal system that sustains elevated repetitive reverse voltage while keeping leakage current low for a small-signal Schottky. This is why ST positions the part specifically for telecommunication line-card SLIC protection: during hot insertion of the line card, the SLIC rings/line drivers see voltage transients that the Schottky clamps and rectifies without introducing switching spikes.
Typical applications include SLIC and line-card protection in telecom exchange equipment, low-power output rectification in auxiliary switching supplies, reverse-polarity and free-wheeling protection, and small-signal detection and clamping circuits. The SOT-23 package allows dense automated assembly.
In design, verify the reverse-leakage increase with junction temperature; Schottky leakage roughly doubles every 10C, so derate for hot environments. Confirm the A-version voltage rating matches your worst-case line transient before drop-in substitution from the BAR46 base grade.
This page synthesizes distributor listings, datasheet-derived specifications, drop-in alternatives, and design guidance not consolidated in the manufacturer datasheet alone.
Drop-in alternatives for BAR46A β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with BAR46A (same form factor and footprint) β differing in Package, Technology, Diode Configuration, Forward Voltage (VF), Maximum Operating Temperature.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
BAR46AFILM
β Drop-In β οΈ εζ°εΎ ιͺθ―β In Stock
$0.032 / Unit
View Datasheet βBAR46AFILM
β Drop-Inβ In Stock
$0.032 / Unit
View Datasheet βKAR46A
β Drop-Inπ Reference alternative (not in catalog)
BAT46WH
β Drop-In β οΈ εζ°εΎ ιͺθ―β In Stock
$0.029 / Unit
View Datasheet βBAT54
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
BAR46A Maximum Ratings & Electrical Characteristics
| Product Type | Small Signal Schottky Diode |
| Configuration | Schottky rectifier (BAR46A version, high voltage) |
| Package | SOT-23 |
| Mounting Type | Surface Mount |
| Forward Voltage Drop (VF) | Low forward voltage drop (typical value per datasheet curve) |
| Switching Losses | Negligible (Schottky junction, no reverse recovery) |
| Conduction Losses | Very small (per ST datasheet features) |
| Primary Application | SLIC protection during card insertion |
| Technology | Schottky barrier |
| Related Family Members | BAR46, BAR46AFILM, KAR46A equivalent |
| RoHS Status | Compliant |
| Datasheet Length | 5 pages (49 KB PDF) |
BAR46A Pin Configuration
| Pin 1 | A β Anode of the Schottky diode (per BAR46A datasheet schematic) |
| Pin 2 | K2 β Cathode terminal 2 (per BAR46A datasheet schematic) |
| Pin 3 | K1 β Cathode terminal 1 (per BAR46A datasheet schematic) |
Typical Applications
BAR46A is suitable for 6 applications: SLIC Protection in Telecom Line Cards, Low-Power Switching Supply Output Rectification, Reverse Polarity and Input Protection, Signal Clamping and Detection Circuits, Battery-Powered and Portable Equipment, Industrial Control Board Freewheeling and Clamping.
SLIC Protection in Telecom Line Cards
The BAR46A is explicitly designed by STMicroelectronics for SLIC (Subscriber Line Interface Circuit) protection during card insertion operations in telecom exchange equipment. During hot insertion, ring and tip lines can present voltage transients well above normal operating levels; the BAR46A's high repetitive reverse voltage rating clamps these events while its Schottky junction contributes negligible switching losses and very small conduction losses. Placed between the line protection network and the SLIC IC supply rails, the diode rectifies and blocks without adding reverse-recovery spikes that could corrupt the sensitive analog line interface. Its SOT-23 SMD footprint supports dense line-card layouts with automated assembly.
Recommended
Low-Power Switching Supply Output Rectification
In auxiliary and standby switching converters, the BAR46A serves as an output or freewheeling rectifier where its negligible switching losses directly improve efficiency at moderate switching frequencies. Because a Schottky junction stores no reverse-recovery charge, the diode turns off cleanly with no recovery current spike, reducing both switching loss and EMI compared with a fast-recovery P-N diode. The very small conduction losses keep the forward-power term low at the small-signal current levels typical of bias and standby rails. Verify the reverse voltage margin against the converter's worst-case flyback or off-state voltage, and confirm leakage at elevated junction temperature in sealed enclosures.
Recommended
Reverse Polarity and Input Protection
Series-connected in a supply input path, the BAR46A blocks reverse polarity with its high reverse-voltage rating while adding only a low forward voltage drop in normal operation, preserving headroom in low-voltage electronics. Compared with a standard silicon rectifier, the Schottky's low VF reduces the voltage budget consumed by protection - meaningful in 3.3V and 5V systems where every few hundred millivolts count. Because the part is a small-signal device, size it only for the continuous input current of low-power equipment; for higher current paths use a power Schottky in a larger package. The SOT-23 footprint drops onto standard SMD land patterns without PCB redesign.
Recommended
Signal Clamping and Detection Circuits
In small-signal detection, envelope detection, and precision clamping networks, the BAR46A's low forward voltage drop lowers the conduction threshold, improving sensitivity at low signal amplitudes. The absence of reverse recovery means the diode does not inject charge back into high-impedance nodes when the signal reverses - important in measurement front ends and RF envelope detectors. ST's high-barrier Schottky metal system keeps leakage moderate for the class, though designers should still verify leakage at temperature in high-impedance applications. The 3-pin SOT-23 with an NC terminal (BAR46) or dual-terminal set (BAR46A) allows flexible routing on dense analog boards.
Recommended
Battery-Powered and Portable Equipment
In battery-operated equipment, the BAR46A works as an ORing or charging-path diode where its low forward voltage drop minimizes the voltage lost between battery and load, extending usable battery life versus conventional silicon diodes. Very small conduction losses translate to less heat in compact enclosures, and negligible switching losses matter in pulsed-load topologies. The high reverse-voltage rating provides margin against charger transients and inductive kick from motors or relays sharing the battery bus. For leakage-sensitive designs, confirm the Schottky reverse leakage at the maximum expected ambient temperature, since Schottky leakage rises steeply with temperature and can matter in multi-week standby scenarios.
Recommended
Industrial Control Board Freewheeling and Clamping
On industrial control boards, the BAR46A clamps inductive kick from small relays, solenoids, and buzzers, protecting low-side driver transistors from overvoltage. Its Schottky junction reacts instantly - there is no forward-recovery delay - so the clamp engages on the first edge of the flyback event, keeping drain or collector overshoot tight. The high reverse-voltage rating withstands repeated clamping cycles, and the SOT-23 package fits beside each relay driver footprint. For larger relays or solenoids with energy beyond the small-signal diode's rating, specify a power rectifier instead; the BAR46A is optimized for the small-coil, low-current clamping typical of telecom and instrumentation relays.
Recommended
Recommended Products Summary
Engineering reference data for BAR46A β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BAR46 | BAR46AFILM | KAR46A | BAT46 |
|---|---|---|---|---|---|
| Package | SOT-23 | SOT-23 - same | SOT-23 - same | SOT-23 - same | SOT-23 - same |
| Brand | STMicroelectronics | STMicroelectronics | STMicroelectronics | STMicroelectronics (cross-referenced equivalent) | STMicroelectronics |
| Technology | Schottky barrier, high voltage | Schottky barrier | Schottky barrier (FILM process) | Schottky barrier | Schottky barrier |
| Reverse Voltage Rating | High voltage (A version, exact VRRM per datasheet) | Lower than A version | Same as BAR46A | Same as BAR46A | 45 V class |
| Switching Losses | Negligible | Negligible | Negligible | Negligible | Negligible |
| Forward Voltage Drop | Low | Low | Low | Low | Low (higher current class) |
| Primary Application | SLIC protection during card insertion | General small-signal Schottky | Automotive SLIC/protection | Equivalent SLIC protection | General rectification, higher current |
| Qualification | Standard industrial/consumer | Standard | Automotive FILM process | Standard | Standard |
Key Differentiators
- Higher reverse-voltage margin for SLIC line transients (vs BAR46)
- Automotive process option available (vs BAR46)
- Higher-current alternative exists in same footprint (vs BAT46)
Design Notes
Do not substitute the base BAR46 for the BAR46A in SLIC protection positions. The A version exists specifically because line-card insertion transients can exceed the base version's reverse voltage rating, leading to avalanche stress or destructive breakdown. Before any drop-in substitution (BAR46, BAT46, KAR46A), verify the repetitive reverse voltage and average rectified forward current on the specific datasheet revision - parameters may vary slightly between manufacturers of the same generic part number, as cross-reference aggregators explicitly warn.
Schottky reverse leakage approximately doubles every 10C of junction temperature rise. In sealed telecom shelves or outdoor cabinets where ambient can reach 70C or more, the BAR46A's off-state leakage will be orders of magnitude above the 25C datasheet value. Estimated: at a typical VF of a few hundred millivolts and small-signal forward currents, self-heating is minimal, but board-level hotspots near drivers should be checked. Budget leakage into any high-impedance or battery-standby node connected to the diode.
The SOT-23 land pattern is standardized, so footprint reuse across BAR46, BAR46A, BAR46AFILM, and BAT46 is safe. Keep the diode close to the node being clamped - especially in SLIC protection, where long traces add inductance that lets voltage overshoot build before the diode conducts. For clamping applications, place the diode directly across the protected coil or line terminal with short, wide returns. No heatsinking is needed at small-signal currents; the SOT-23 leads dissipate heat adequately on standard 1 oz copper.
Compliance Information
RoHS compliance assumed per standard ST SOT-23 diode offering; full REACH/halogen detail should be confirmed on the ST product page for the BAR46 family.
