BSP129H6327XTSA1 - 240V N-Ch Depletion MOSFET | Infineon | SOT-223
MPN: BSP129H6327XTSA1 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.85 | $0.85 |
| 10 | $0.72 | $7.20 |
| 100 | $0.58 | $58.00 |
| 500 | $0.46 | $230.00 |
| 1,000 | $0.38 | $380.00 |
| 3,000 | $0.3 | $900.00 |
BSP129H6327XTSA1 Overview
A depletion-mode MOSFET is a field-effect transistor in which the conducting channel is physically present at fabrication and is narrowed by applying a reverse gate-source bias; removing the bias or applying a forward bias widens the channel. This is the opposite of an enhancement-mode MOSFET, which requires a gate bias to create the channel. Depletion-mode devices therefore act as normally-on switches and are commonly used where fail-safe conduction is required or where a bias-free current path must be maintained. The BSP129 sits inside the broader taxonomy: N-channel MOSFET -> power MOSFET -> discrete semiconductor -> semiconductor device. Its key synonyms in design documents are "normally-on N-MOSFET" and "depletion-mode small-signal transistor."
Key features include a 240 V drain-source breakdown voltage, 350 mA continuous ID at TA = 25 C, a maximum on-resistance of 4.2 ohm (some sources list 6 ohm), 1.8 W power dissipation at TA, dv/dt ruggedness, and AEC-Q101 automotive qualification. The 4-pin SOT-223 package provides a thermal pad that doubles as the drain terminal, enabling direct PCB copper heatsinking.
Technically, the BSP129 uses Infineon's vertical SIPMOS process, which delivers high breakdown voltage in a small die area. The depletion-mode construction is implemented through precise channel doping rather than gate-oxide engineering, giving the device its characteristic negative-VGS(off) threshold. Because the channel is present at zero bias, designers must consider that the device will conduct in a power-down state if used as a low-side switch.
Typical applications include active loads and constant-current sources in linear power supplies, high-side startup bypass paths, automotive ECU bias circuits, e-fuse pre-charge stages, and bias generators for gate-driver ICs. The AEC-Q101 qualification broadens its use into automotive body and lighting modules.
Designers should treat the thermal tab (pin 4) as the drain and tie it to a copper pour sized for the expected dissipation. When using the BSP129 as a constant-current source, place the source resistor close to the source pin and add a gate-source resistor to set the operating point; the negative threshold means a small positive VGS can fully enhance the channel and lower RDS(on).
This page synthesizes distributor stock and pricing data, drop-in same-package alternatives, and practical bias-circuit design notes that go beyond the manufacturer datasheet narrative.
Drop-in alternatives for BSP129H6327XTSA1 — 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 BSP129H6327XTSA1 (same form factor and footprint) — differing in Package, Drain-Source Voltage (VDS), FET Type, MSL Level, Operating Temperature Range.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
BSP129H6327
✅ Drop-In📋 Reference alternative (not in catalog)
BSP92PH6327XTSA1
✅ Drop-In✓ In Stock
$0.31 / Unit
View Datasheet →BSP135H6327XTSA1
✅ Drop-In✓ In Stock
$0.43 / Unit
View Datasheet →BSP135H6906XTSA1
✅ Drop-In✓ In Stock
$0.78 / Unit
View Datasheet →BSL308CH6327XTSA1
✅ Drop-In✓ In Stock
$0.21 / Unit
View Datasheet →BSS127H6327XTSA2
✅ Drop-In✓ In Stock
$0.032 / Unit
View Datasheet →BSP129H6327XTSA1 Maximum Ratings & Electrical Characteristics
| FET Type | N-Channel, Depletion Mode |
| Drain-Source Voltage (VDS) | 240 V |
| Continuous Drain Current (ID) at TA=25C | 350 mA |
| On-Resistance RDS(on) max | 4.2 ohm (some sources 6 ohm) |
| Power Dissipation (PD) at TA=25C | 1.8 W |
| Package | PG-SOT223-4 (SOT-223, 3+Tab) |
| Mounting Type | Surface Mount |
| Operating Temperature | -55 C to +150 C (junction) |
| dv/dt Ruggedness | Yes (rated) |
| Automotive Qualification | AEC-Q101 qualified |
| RoHS Status | Compliant |
| Lead-Free | Yes |
| Process Technology | SIPMOS (vertical DMOS) |
| Drain Terminal | Tab (pin 4) |
BSP129H6327XTSA1 Pin Configuration
| Pin 1 | GATE — Gate control input (negative VGS to turn off) |
| Pin 2 | DRAIN — Drain terminal (internally bonded to tab) |
| Pin 3 | SOURCE — Source terminal (return for gate drive and load) |
| Pin 4 | DRAIN (TAB) — Drain tab - thermal pad and primary drain connection |
Safe Operating Area (DC, TA = 25 C)
Typical Applications
BSP129H6327XTSA1 is suitable for 6 applications: Constant-Current Source / Active Load, High-Side Startup / Pre-charge Bypass, Automotive ECU Bias Circuit, Gate-Driver Bootstrap Bias, Linear Regulator Active Load (Test), Solid-State Relay (SSR) Input Stage.
Constant-Current Source / Active Load
The BSP129H6327XTSA1's depletion-mode channel makes it the textbook transistor for simple, low-part-count constant-current sources. With the gate tied to the source through a bias resistor and a small source resistor (RS) to ground, the device self-biases to a near-constant drain current set by the depletion threshold and the source resistor. The 240 V VDS rating means it can sit directly across a high-voltage rail, while the 4.2 ohm RDS(on) keeps dissipation modest at 10-50 mA bias levels. This circuit is preferred over op-amp + pass-MOSFET designs when cost or simplicity matters and accuracy within 10-20 percent is acceptable, such as zener bias, reference stack excitation, or LED string drivers.
Recommended
High-Side Startup / Pre-charge Bypass
Because the BSP129H6327XTSA1 is normally-on, it can serve as a fail-safe high-side startup path that conducts before any controller comes alive. Designers place it in parallel with the main high-side switch to provide initial charging of a bootstrap capacitor or to keep a downstream LDO alive during cold-crank events. The 350 mA ID rating and 240 V VDS comfortably cover 12 V and 24 V automotive bus pre-charge waveforms, and the AEC-Q101 qualification makes the part acceptable for body-control modules. Once the main controller is up, it can either leave the BSP129 conducting or actively drive the gate negative to fully turn it off.
Recommended
Automotive ECU Bias Circuit
The BSP129H6327XTSA1's AEC-Q101 qualification, 240 V transient tolerance, and depletion-mode behavior suit it to automotive ECU bias networks where the part must remain conducting through 12 V crank and load-dump transients. The dv/dt ruggedness allows the device to ride through relay-induced transients without latch-up. A typical bias arrangement places the BSP129 between a 12 V protected rail and a series resistor feeding a 5 V LDO, providing a high-impedance source that limits inrush and isolates upstream noise. The SOT-223 tab connects to a small copper pour for thermal dissipation under the 1.8 W rating.
Recommended
Gate-Driver Bootstrap Bias
Half-bridge and three-phase gate drivers (such as the IRS21064 or IRS2184 families) require a floating bootstrap supply that is recharged every switching cycle. The BSP129H6327XTSA1 can be used as a depletion-mode pass device that continuously trickle-charges the bootstrap capacitor through a small diode, supplementing the standard bootstrap diode and ensuring the high-side driver never starves during long 100 percent duty cycles. Its 240 V rating comfortably exceeds the rectified bus voltages used in motor drives and Class D audio amplifiers. Because it is normally-on, the bootstrap stays primed even if the controller has not yet issued switching commands.
Recommended
Linear Regulator Active Load (Test)
In bench test setups and ATE, an active load is often preferred to a passive resistor because it can sweep current electronically while presenting a fixed sink voltage. The BSP129H6327XTSA1 makes a compact, low-cost active load: gate driven by an op-amp that senses a current-sense resistor in the source path. The depletion mode lets the load start conducting at zero gate drive command, avoiding the dead zone that enhancement-mode active loads exhibit at very low currents. The 240 V and 350 mA ratings comfortably cover 3.3 V, 5 V, 12 V, and 24 V rail testing for both linear and switching regulators.
Recommended
Solid-State Relay (SSR) Input Stage
The depletion-mode behavior of the BSP129H6327XTSA1 lets it act as the input stage of a low-power solid-state relay where the control signal is the gate bias. With VGS = 0, the device conducts and energizes the output (typically an optocoupler LED or a small triac driver); applying a negative VGS forces it off. Combined with the 240 V transient rating and AEC-Q101 qualification, this arrangement is well suited to automotive SSR modules and industrial interface cards that must operate across wide temperature and voltage swings. The SOT-223 footprint keeps the part compact alongside the output opto or triac.
Recommended
Recommended Products Summary
Engineering reference data for BSP129H6327XTSA1 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BSP129H6327 | BSP92PH6327XTSA1 | BSP135H6327XTSA1 | BSP135H6906XTSA1 | BSL308CH6327XTSA1 | BSS127H6327XTSA2 |
|---|---|---|---|---|---|---|---|
| Brand | Infineon Technologies | Infineon Technologies | Infineon Technologies | Infineon Technologies | Infineon Technologies | Infineon Technologies | Infineon Technologies |
| Package | SOT-223 (3+Tab) | SOT-223 (3+Tab) - same | SOT-223 (3+Tab) - same | SOT-223 (3+Tab) - same | SOT-223 (3+Tab) - same | SOT-223 (3+Tab) - same | SOT-223 (3+Tab) - same |
| FET Type | N-Channel Depletion | N-Channel Depletion | P-Channel Depletion | N-Channel Depletion | N-Channel Depletion | N-Channel Enhancement (not equivalent mode) | N-Channel Depletion |
| Drain-Source Voltage (VDS) | 240 V | 240 V | 250 V | 600 V | 600 V | 30 V | 600 V |
| Continuous Drain Current (ID) | 350 mA | 350 mA | 260 mA | 250 mA | 250 mA | 2.3 A | 250 mA |
| Power Dissipation | 1.8 W | 1.8 W | 1.8 W | 1.8 W | 1.8 W | 2.0 W | 1.8 W |
| Automotive Qualification | AEC-Q101 | AEC-Q101 | AEC-Q101 | AEC-Q101 | AEC-Q101 | AEC-Q101 | AEC-Q101 |
| Unit Price (qty 1, USD) | 0.85 | ~0.85 | ~0.90 | ~0.95 | ~0.95 | ~0.60 | ~0.55 |
Key Differentiators
- Depletion-mode (normally-on) behavior (vs BSL308CH6327XTSA1)
- Lower RDS(on) than higher-voltage depletion alternatives (vs BSP135H6327XTSA1)
- N-channel polarity matches standard high-side topologies (vs BSP92PH6327XTSA1)
Design Notes
Estimated: at full 350 mA ID and 50 V VDS the part dissipates roughly 350 mA x 50 V x (RDS(on)/VDS) - i.e. the dominant loss is conduction: I^2 x RDS(on). At 350 mA and 4.2 ohm RDS(on), conduction loss is ~0.5 W, well below the 1.8 W package rating. Solder the tab to at least 100 mm^2 of 1 oz copper to keep theta_JA near the datasheet 80 C/W typical value, and derate linearly above TA = 25 C.
Do NOT substitute an enhancement-mode MOSFET in place of the BSP129H6327XTSA1 without redesigning the bias network. The depletion-mode channel is normally-on, so the device will conduct with VGS = 0 and must be turned off with a negative gate bias. In constant-current-source circuits, removing the gate-source resistor disables the bias point and the load current collapses - design the gate network first, then the current-setting resistor.
Place a 100 ohm gate resistor in series with the gate pin to suppress high-frequency oscillation caused by the package's lead inductance combined with the gate-drain capacitance. Keep gate traces short and route them away from drain switching nodes. Tie the SOT-223 tab to a copper pour that is at least 50 mm^2 to stay within the 1.8 W rating; without the pour, dissipation must be derated by ~50 percent.
Keep the source-trace return path short and wide. In constant-current-source applications, the source resistor must be Kelvin-connected to the source pin to avoid ground-loop errors that otherwise shift the bias current. For high-voltage (>100 V) applications, maintain at least 0.5 mm clearance between the drain tab and any low-voltage trace to satisfy typical IEC 60950 / IPC-2221 creepage requirements.
Compliance Information
AEC-Q101 (automotive discrete) qualification per Infineon datasheet summary; RoHS compliant per distributor listings. Halogen-free status not confirmed in provided data.
