BAT42-TAP - 30V 200mA Schottky Diode DO-35 | Vishay
MPN: BAT42-TAP ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.09 | $0.09 |
| 10 | $0.07 | $0.70 |
| 100 | $0.053 | $5.30 |
| 500 | $0.045 | $22.50 |
| 1,000 | $0.035 | $35.00 |
BAT42-TAP Overview
A Schottky diode replaces the conventional P-N junction with a metal-semiconductor barrier, producing a very low turn-on voltage and near-zero reverse recovery time. Within the voltage regulator and rectifier family hierarchy, small-signal Schottky diodes such as the BAT42 serve as high-speed switching, freewheeling, polarity-protection, and detection elements in signal-level circuits.
Key features include very low forward turn-on voltage compared to silicon junction diodes, extremely fast switching for high-frequency operation, and an integrated P-N junction guard ring that protects the metal-silicon junction against excessive voltage events such as electrostatic discharge. The Mouser listing also documents a surge current rating of 4.0 A (IFSM), giving robust tolerance for short-duration transient overloads.
The DO-35 package is hermetically sealed glass, providing superior long-term reliability and moisture immunity versus many molded packages, and its axial leads support both wave soldering and hand assembly. Vishay also offers the BAT42 die in SOD-123 surface-mount form (BAT42W series) and MiniMELF variants, but this -TAP version targets legacy through-hole boards, repairs, and hobby prototypes.
Typical applications include small-signal high-speed switching, polarity guard and reverse-battery protection, freewheeling clamps in low-current relay and motor-driver circuits, RF detection envelopes, and general-purpose rectification on 5 V and 12 V analog rails.
Design consideration: because the BAT42-TAP is a small-signal part, verify that continuous load current stays at or below 200 mA and that surge energy remains within the 4 A IFSM envelope; for higher current, step up to BAT85-class or power Schottky parts.
This page synthesizes verified distributor listings, cross-reference data, drop-in alternatives, and practical design notes not consolidated in the manufacturer datasheet.
Drop-in alternatives for BAT42-TAP — 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 BAT42-TAP (same form factor and footprint) — differing in Package, Diode Type, Switching Speed, Mounting Type, ESD Protection.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
BAT43-TAP
✅ Drop-In📋 Reference alternative (not in catalog)
BAT41-TAP
✅ Drop-In✓ In Stock
$0.028 / Unit
View Datasheet →BAT43
✅ Drop-In✓ In Stock
$0.08 / Unit
View Datasheet →BAT42
✅ Drop-In✓ In Stock
$0.02 / Unit
View Datasheet →1N5711
✅ Drop-In✓ In Stock
$0.18 / Unit
View Datasheet →BAT42-TAP Maximum Ratings & Electrical Characteristics
| Diode Type | Small-Signal Schottky Barrier |
| Repetitive Peak Reverse Voltage (VRRM) | 30 V |
| Average Forward Current (IF(AV)) | 200 mA |
| Non-Repetitive Surge Current (IFSM) | 4.0 A |
| Reverse Recovery | Fast switching (Schottky, no stored charge) |
| Package | DO-204AH (DO-35) glass axial |
| Mounting Type | Through Hole |
| Termination Style | Axial Leads |
| Packaging Suffix | -TAP (Ammo tape packing) |
| Configuration | Single Diode |
| Protection Feature | PN junction guard ring against ESD / excessive voltage |
| AEC-Q101 Option | Qualified version available on request |
| RoHS Status | Compliant |
| Mounting Technology | Wave solder / hand solder |
BAT42-TAP Pin Configuration
| Pin 1 | Anode — Positive terminal; current flows into the diode when forward biased |
| Pin 2 | Cathode — Marked terminal; identified by the band printed on the DO-35 glass body |
Typical Applications
BAT42-TAP is suitable for 6 applications: High-Speed Small-Signal Switching, Reverse Polarity and Battery Protection, Freewheeling Clamp for Relays and Small Motors, RF and Signal Detection Envelope, Diode OR-ing of Auxiliary Supplies, Through-Hole Repair and Legacy Board Service.
High-Speed Small-Signal Switching
The BAT42-TAP fits high-speed signal switching because a Schottky barrier stores essentially no minority-carrier charge, so it switches in the nanosecond range with no reverse-recovery delay, unlike standard silicon junction diodes. In clamp, steering, and gating circuits on 5 V or 12 V logic-level rails, the low turn-on voltage also reduces signal loss in series-diode paths. Used as a directional steering or OR-ing element between two logic supplies, the diode conducts at a low forward voltage, preserving noise margin. Engineers should keep continuous current at or below the 200 mA rating and use short leads in the DO-35 package to limit loop inductance in fast edges.
Recommended
Reverse Polarity and Battery Protection
In battery-powered and handheld equipment, the BAT42-TAP provides series reverse-polarity protection: if the battery is inserted backwards, the diode blocks and the load sees zero volts, while in correct polarity the Schottky's low forward voltage drops only a few hundred millivolts, preserving battery run time compared with a silicon diode losing about 0.7 V. On 12 V systems the 30 V VRRM gives adequate margin against inductive kick. The guard-ring construction adds robustness against ESD during battery insertion and handling. For currents up to 200 mA this is a minimal-parts-cost solution; above that, choose a power Schottky in DO-41 or larger packages to stay within the safe thermal envelope.
Recommended
Freewheeling Clamp for Relays and Small Motors
When a relay coil, small solenoid, or low-current DC motor is switched off, the collapsing magnetic field drives an inductive voltage spike that would otherwise avalanche or destroy the driving transistor. A BAT42-TAP placed across the coil, cathode to the positive rail, clamps the spike while conducting the decay current. The Schottky's fast turn-on and absence of reverse recovery shorten the release time versus a 1N400x freewheel, improving relay cycle rate. The 4.0 A IFSM rating absorbs the initial clamp surge. This suits coil currents up to roughly 200 mA; for larger relays, size the diode to the coil current and consider a BAT85 or SB-series part.
Recommended
RF and Signal Detection Envelope
The low barrier and low junction capacitance of the BAT42 make it usable as an envelope detector and small-signal rectifier in RF front ends, crystal-radio-style demodulators, and measurement probes at HF to lower-VHF frequencies. Because the metal-silicon junction begins conducting at a lower forward voltage than a P-N diode, weak detected signals produce a larger usable output, improving sensitivity. The DO-35 glass body with trimmed axial leads keeps parasitics modest, though lead length should be minimized at the highest operating frequencies. For precision RF power measurement at VHF and above, verify capacitance limits against the datasheet curves and consider dedicated detector diodes if sensitivity requirements are extreme.
Recommended
Diode OR-ing of Auxiliary Supplies
In systems combining a main supply with a backup source, such as a wall adapter with battery backup on a memory-retention rail, a BAT42-TAP per source forms a simple diode-OR. The Schottky's low forward drop reduces the voltage penalty between sources and load, and its fast switching prevents current back-feed during source switchover transients. This suits retention currents and low-power standby loads up to 200 mA; the 30 V rating covers 5 V, 12 V, and most single-cell stack scenarios with margin. For precision designs, account for forward-voltage variation with current and temperature, or replace the diode with an ideal-diode controller where every millivolt matters.
Recommended
Through-Hole Repair and Legacy Board Service
The axial DO-35 glass package of the BAT42-TAP matches millions of legacy through-hole PCBs where a small-signal Schottky was originally installed. Replacement during repair is mechanical as well as electrical: lead spacing, lead diameter, and glass-body dimensions are industry-standard, so the part fits existing holes and lead-bend fixtures without rework. The hermetic glass package tolerates repeated soldering operations better than molded parts, and the ammo tape format feeds automated insertion lines during production repair runs. Service engineers should verify the 30 V and 200 mA limits against the original design and keep soldering iron contact below the manufacturer's recommended time-temperature profile to protect the die attach.
Recommended
Recommended Products Summary
Engineering reference data for BAT42-TAP — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BAT43-TAP | BAT41-TAP | BAT43 (ST) | 1N5711 |
|---|---|---|---|---|---|
| Package | DO-204AH (DO-35) axial | DO-204AH (DO-35) axial - same | DO-204AH (DO-35) axial - same | DO-204AH (DO-35) axial - same | DO-204AH (DO-35) axial - same |
| Brand | Vishay Intertechnology | Vishay Intertechnology | Vishay Intertechnology | STMicroelectronics | onsemi |
| Reverse Voltage (VRRM) | 30 V | 30 V | 100 V | 30 V | 70 V |
| Forward Current | 200 mA | 200 mA | 200 mA | 200 mA | 15 mA (small-signal detector class) |
| Switching Speed | Fast (Schottky, no reverse recovery) | Fast (Schottky) | Fast (Schottky) | Fast (Schottky) | Fast (Schottky, RF class) |
| Typical Use Case | Low-VF small-signal switching / protection | General-purpose low-frequency rectification | Higher-voltage (up to 100 V) small-signal duty | Cross-brand general-purpose replacement | UHF mixer/detector, higher-voltage low-current |
Key Differentiators
- Lowest forward turn-on voltage in the DO-35 family line-up (vs BAT41-TAP)
- Lower junction capacitance than BAT43 (vs BAT43-TAP)
- Much lower forward drop than 1N5711 (vs 1N5711)
- Hermetic glass DO-35 reliability versus SOD-123 molded part (vs BAT42W-V)
Design Notes
Keep the average forward current at or below 200 mA and the peak reverse voltage below 30 V with derating margin - in practice target no more than 80% of ratings, so about 160 mA and 24 V. Estimated: at a forward drop of roughly 0.4 V and 200 mA, conduction dissipation is about 80 mW, which the DO-35 glass body handles comfortably with standard lead length; longer leads only improve heat escape. Exceeding current raises junction temperature and leakage rapidly because Schottky reverse leakage roughly doubles every 10 C.
For through-hole assembly, keep axial lead bends at least 2 mm from the glass body and use pliers or a bending fixture - direct force on the glass-to-metal seal cracks the hermetic package. During hand soldering, use a heat sink (long-nose pliers) between the body and the joint and limit iron contact to a few seconds, since repeated thermal shock degrades the die attach. Wave-solder profiles per IPC general guidance are safe for DO-35 glass; verify against your board's thermal mass.
Two frequent mistakes with BAT42-TAP: first, substituting a standard junction diode like 1N4148 in freewheeling or fast-switching positions restores reverse-recovery delay and lengthens relay release times - the whole point of BAT42 is the Schottky's zero stored charge. Second, using it as a power rectifier on transformer secondaries above a few hundred milliamps leads to thermal runaway from rising leakage. Also note reverse leakage is higher than a silicon diode, so in ultra-low-power battery circuits measure actual leakage in-circuit before committing.
Compliance Information
RoHS compliance per distributor listings for the active BAT42-TAP. Vishay datasheet states an AEC-Q101-qualified version is available under a part number on request; the standard BAT42-TAP is commercial grade.
