BAT43 - 30V 200mA Schottky Diode DO-35 | STMicroelectronics
MPN: BAT43 β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.32 | $0.32 |
| 10 | $0.26 | $2.60 |
| 100 | $0.15 | $15.00 |
| 500 | $0.11 | $55.00 |
| 1,000 | $0.08 | $80.00 |
BAT43 Overview
A Schottky diode is a metal-to-silicon rectifier in which a metal-semiconductor junction replaces the P-N junction of a conventional diode. This structure eliminates reverse-recovery charge, so switching is inherently fast, and the forward voltage drop (typically around 0.3-0.4 V at moderate currents for this class) is substantially lower than silicon P-N diodes. Within the power-management hierarchy, the BAT43 belongs to the small-signal Schottky diode family, sitting under general-purpose rectifiers and discrete semiconductors.
Key electrical parameters from the STMicroelectronics datasheet include: 30 V VRRM, 200 mA continuous forward current at Ta = 25 C, 500 mA repetitive peak forward current (tp <= 1 s, delta <= 0.5), 4 A non-repetitive surge current (IFSM, tp = 10 ms), and 200 mW power dissipation at Tl = 65 C. These figures make it well suited to low-power signal rectification, polarity protection, and detection duties.
The DO-35 glass body is hermetically sealed, giving the device excellent long-term reliability and stable junction characteristics over temperature. The through-hole leads suit hand assembly, prototyping, repair, and hobby construction as well as low-density industrial boards. Surface-mount equivalents in SOD-123 (BAT42W-V to BAT43W-V) and MiniMELF cases exist within the same ST family for automated assembly.
Typical applications include low-frequency and RF signal detection, reverse-polarity and battery protection clamps, ORing of low-voltage supplies, and free-wheeling or clamping roles in low-current switching circuits where the low forward drop improves efficiency.
Design consideration: respect the 30 V reverse rating with adequate margin - derate for supply transients, and note the 200 mW dissipation limit when running near full current.
This page synthesizes distributor availability data, cross-brand equivalents, and practical design notes not found in the manufacturer datasheet.
Drop-in alternatives for BAT43 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 BAT43 (same form factor and footprint) β differing in Package, Diode Type, ESD Protection, Switching Speed, Reverse Recovery.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
BAT42
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$0.02 / Unit
View Datasheet βBAT41
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$0.028 / Unit
View Datasheet βBAT48
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Contact for price
View Datasheet βBAT45
β Drop-Inπ Reference alternative (not in catalog)
BAT43
β Drop-Inβ In Stock
$0.08 / Unit
View Datasheet βBAT43
β Drop-Inβ In Stock
$0.08 / Unit
View Datasheet βBAT43 Maximum Ratings & Electrical Characteristics
| Device Type | Small Signal Schottky Diode |
| Repetitive Peak Reverse Voltage (VRRM) | 30 V |
| Forward Continuous Current (IF) | 200 mA at Ta = 25 C |
| Repetitive Peak Forward Current (IFRM) | 500 mA (tp <= 1 s, delta <= 0.5) |
| Non-Repetitive Surge Current (IFSM) | 4 A (tp = 10 ms) |
| Power Dissipation (Ptot) | 200 mW at Tl = 65 C |
| Technology | Metal-to-silicon Schottky barrier |
| ESD Protection | Integrated guard ring against excessive voltage |
| Package | DO-35 (glass axial, through-hole) |
| Mounting Type | Through Hole |
| Case Style | Hermetically sealed glass body |
| Configuration | Single diode |
BAT43 Pin Configuration
| Pin 1 | Anode β Forward current enters; connect toward positive potential for conduction |
| Pin 2 | Cathode β Marked by band on DO-35 glass body; blocks reverse voltage up to 30 V |
Typical Applications
BAT43 is suitable for 6 applications: Low-Voltage Signal Rectification, Reverse Polarity Protection, Diode ORing of Low-Voltage Supplies, Clamping and Free-Wheeling in Low-Current Switching Circuits, Prototyping, Repair and Hobby Electronics, ESD-Robust Input Protection.
Low-Voltage Signal Rectification
The BAT43's very low Schottky turn-on voltage makes it a strong fit for rectifying small AC and audio-frequency signals where a silicon P-N diode's 0.6-0.7 V drop would destroy the signal. With a 200 mA continuous forward current rating, it handles detector and rectifier duties in signal chains, instrumentation front ends, and measurement bridges. Its fast switching - inherent to the metal-to-silicon junction with no reverse-recovery charge - keeps switching losses negligible at typical signal frequencies. In precision detectors, the low forward drop improves sensitivity and dynamic range; designers should still account for the Schottky's higher reverse leakage at elevated temperature when accuracy at low signal levels matters.
Recommended
Reverse Polarity Protection
Placing a BAT43 in series with a low-voltage supply rail provides simple reverse-polarity protection with minimal voltage loss: the very low forward voltage preserves headroom on 3.3 V and 5 V logic supplies, where a conventional diode's drop would be costly. The 200 mA continuous rating covers typical sensor nodes, remote controls, and small embedded boards, while the 4 A surge rating absorbs short inrush events such as bulk-capacitor charging at plug-in. The 30 V VRRM withstands the reverse voltage applied during a polarity fault on 5 V and low-side 12 V systems. Above roughly 150-200 mA continuous, or for higher rails, a power Schottky rectifier should be used instead.
Recommended
Diode ORing of Low-Voltage Supplies
Two BAT43 diodes can OR the outputs of a battery and an adapter (or two adapters) feeding a low-power load. Because the Schottky junction's very low turn-on voltage wastes less headroom than silicon P-N diodes, the load sees a higher effective supply and the battery life improves. The 30 V rating comfortably covers 5 V and low-side 12 V ORing scenarios, and the guard-ring ESD protection adds robustness at connector-exposed inputs. Key trade-off: Schottky reverse leakage is higher than P-N diodes, which slightly discharges the idle battery through the diode; this is acceptable for most designs but should be calculated for long shelf-life battery products.
Recommended
Clamping and Free-Wheeling in Low-Current Switching Circuits
In relay drivers, small solenoid circuits, and transistor switching stages up to a few hundred milliamps, the BAT43 serves as a free-wheeling or clamp diode that catches inductive kickback. Its fast Schottky switching - with no reverse-recovery charge - responds quickly to the turn-off transient, and the 4 A non-repetitive surge rating (10 ms) absorbs the stored inductive energy spike. The very low forward voltage also reduces the voltage stress imposed on the switching transistor compared with a standard recovery diode. For larger relays or motors with higher stored energy and continuous currents above 200 mA, step up to a power Schottky such as the 1N5819 class.
Recommended
Prototyping, Repair and Hobby Electronics
The DO-35 glass axial package with through-hole leads makes the BAT43 a natural choice for breadboarding, one-off prototypes, and repair work: it is easy to handle, solder reliably by hand, and visually inspect, and the cathode band prevents polarity mistakes. Its general-purpose 30 V / 200 mA envelope covers the majority of small-signal duties found in consumer and educational circuits - signal detectors, protection clamps, and low-drop rectifiers. The hermetically sealed glass body also resists humidity and aging, so old stock remaining within spec can be trusted after verification. Enthusiast and educational designs benefit from its low forward drop when powering LEDs, detectors, or battery circuits.
Recommended
ESD-Robust Input Protection
The BAT43's integrated guard-ring protection against excessive voltage events such as electrostatic discharge suits it for clamping duties on connector-exposed signal and supply inputs. Used as a clamp to a supply rail, the very low Schottky forward voltage conducts earlier than a P-N diode clamp would, holding input excursions closer to safe levels and protecting sensitive downstream ICs. The 4 A surge capability handles short ESD-class transients, and the hermetic DO-35 package is inherently robust. For boards requiring dense protection arrays in surface mount, the SOD-123 BAT42W-V to BAT43W-V variants provide the same behavior in an automated-assembly format.
Recommended
Recommended Products Summary
Engineering reference data for BAT43 β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BAT42 | BAT45 | BAT43 (Vishay) |
|---|---|---|---|---|
| Package | DO-35 glass axial | DO-35 glass axial - same | DO-35 glass axial - same | DO-35 glass axial - same |
| Brand | STMicroelectronics | STMicroelectronics | STMicroelectronics | Vishay Intertechnology |
| Reverse Voltage (VRRM) | 30 V | 20 V | 45 V | 30 V |
| Forward Current (IF) | 200 mA | 200 mA | Higher current class (see datasheet) | 200 mA |
| Turn-On Voltage Character | Very low (Schottky) | Very low (Schottky) | Low (Schottky) | Very low (Schottky) |
Key Differentiators
- Higher reverse voltage than the closest family member (vs BAT42)
- True low-drop Schottky behavior versus a P-N substitute (vs 1N4148)
- Integrated ESD guard-ring protection (vs Generic commodity Schottky equivalents)
Design Notes
Do not exceed the 30 V repetitive peak reverse voltage (VRRM) - Schottky diodes have no avalanche margin to spare, and inductive spikes on nominally low-voltage rails routinely exceed ratings. In flyback or relay-driver positions, measure or calculate the worst-case reverse voltage including ringing before committing. Also remember Schottky reverse leakage rises steeply with temperature; a BAT43 that leaks acceptably at 25 C can leak orders of magnitude more at 85 C, which matters in battery-ORing and sample-hold circuits.
Respect the 200 mW power dissipation limit specified at a 65 C lead temperature. Estimated: at the full 200 mA continuous current and a typical Schottky forward voltage around 0.4 V, dissipation is about 80 mW (Vf x IF = 0.4 V x 0.2 A), which is within rating at moderate ambient, but verify against the datasheet Vf at your exact current and leave margin for ambient above 65 C. Keep lead lengths short near the body to preserve the lead-solder joint as a heat path.
For through-hole DO-35 assembly, solder within the recommended distance from the glass body and avoid mechanical stress on the leads - glass packages crack under bending forces close to the seal, creating a latent failure path. Bend leads with pliers at least 2 mm from the body. The cathode is identified by the printed band; double-check orientation in protection and ORing roles, since a reversed BAT43 applies full reverse polarity to the load rail.
Compliance Information
Compliance status not stated in the provided web data; verify on the ST product page or distributor environmental listings before specifying for RoHS/REACH-regulated production.
