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onsemi BF421ZL1
- Part No.:
- BF421ZL1
- Manufacturer:
- onsemi
- Category:
- Single Bipolar Transistors
- Package:
- TO-226-3, TO-92-3 Long Body, Formed Leads
- Datasheet:
-
BF421ZL1.pdf
- Description:
- TRANS PNP 300V 0.05A TO92
- Quantity:
- Payment:
- Shipping:
Inventory:8,437
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Product details
Overview
BF421ZL1 from onsemi is a PNP silicon high-voltage transistor rated for −300 VCEO, −300 VCBO, and −5.0 VEBO, with continuous collector current of −500 mA and DC current gain (hFE) ≥50 at −25 mA/−20 V. It operates across −55°C to +150°C and is used in high-voltage switching, relay drivers, and flyback converter output stages.
For engineers reviewing the BF421ZL1 datasheet, pinout, applications, or equivalent options, key selection criteria include its −300 V breakdown rating, TO-92 package thermal resistance (RJA = 150°C/W), saturation voltage (VCE(sat) ≤ −0.5 V at −20 mA/−2.0 mA), and fT = 60 MHz small-signal bandwidth.
Technical Context
The BF421ZL1 is a discrete PNP bipolar junction transistor optimized for high-voltage linear and switching operation. Its design supports stable gain (hFE ≥50) under −25 mA collector current and −20 V collector-emitter bias, with low leakage (ICBO ≤ −0.01 A, IEBO ≤ −100 nA) at rated voltages.
Thermal performance is defined for mounting on FR4 with 200 mm² of 1 oz copper and 5 mm lead length, yielding RJL = 68°C/W and RJA = 150°C/W. Safe operating area (SOA) data confirms capability for pulsed operation up to 10 ms at 1 A/100 V, validated per Figure 5 in the official datasheet.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCEO | −300 V - Maximum sustainable collector-emitter voltage before breakdown in common-emitter configuration |
| hFE | ≥50 - Minimum DC current gain at −25 mA IC, −20 V VCE; ensures reliable base drive sizing |
| VCE(sat) | ≤ −0.5 V - Low saturation voltage at −20 mA IC/−2.0 mA IB; reduces conduction loss in switching |
| fT | 60 MHz - Current-gain bandwidth product at −10 mA IC, −10 V VCE; supports medium-frequency amplification |
| RJA | 150°C/W - Junction-to-ambient thermal resistance on standard FR4 layout; defines power derating slope (6.6 mW/°C above 25°C) |
| IC (cont.) | −500 mA - Continuous collector current rating; sets maximum steady-state load handling capacity |
Pinout & Package
BF421ZL1 is housed in a TO-92 (Case 29, Style 14) plastic package with straight leads in ammo pack configuration. Pin 1 is Emitter, Pin 2 is Collector, Pin 3 is Base - verified per marking diagram and package outline in ON Semiconductor's BF421/D Rev. 5 datasheet.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Emitter) | Current exit terminal for PNP device | Connected to most positive rail in high-side switch configurations; requires proper current-limiting resistor when driven |
| 2 (Collector) | Current entry terminal for PNP device | Typically tied to load and high-voltage supply; handles full switched voltage and current stress |
| 3 (Base) | Control input for minority-carrier injection | Requires negative base current relative to emitter to turn on; base resistor must ensure IB ≥ IC/hFE(min) |
Key Features
| Feature | Design Value |
|---|---|
| Pb-Free, Halogen Free/BFR Free | Complies with RoHS Directive 2011/65/EU and JEDEC JS709B; eliminates hazardous substances without compromising reliability |
| High VCEO (−300 V) | Enables direct interface with 230 VAC-derived rails or flyback transformer secondaries without external snubbing |
| Low VCE(sat) (≤ −0.5 V) | Minimizes power dissipation during saturation, supporting >90% efficiency in low-duty-cycle switching |
| Wide TJ range (−55°C to +150°C) | Validated for industrial and automotive under-hood environments without derating below −40°C or above +125°C |
Applications
| Industrial Relay Drivers | AC-DC Flyback Output Switches |
|---|---|
Use Scenario: Driving electromagnetic relays from microcontroller GPIOs in programmable logic controllers. IC Role / Device Role / Timing Role: High-voltage PNP switch sinking load current from 24–48 VDC rails into ground. Use Value: −300 VCEO withstands inductive kickback spikes; −500 mA IC supports typical 40–100 mA relay coils. | Use Scenario: Primary-side switching element in isolated offline flyback converters delivering 5–24 V outputs. IC Role / Device Role / Timing Role: Fast-turn-off PNP transistor controlling energy transfer to secondary winding. Use Value: 60 MHz fT enables clean switching at 50–100 kHz; SOA curve supports 10 ms pulse handling during startup transients. |
| High-Voltage Linear Regulators | Capacitor Discharge Circuits |
Use Scenario: Pass element in series-regulated supplies powering analog sensors or precision ADCs from 100–300 V sources. IC Role / Device Role / Timing Role: Voltage-controlled current source operating in active region with fixed base bias. Use Value: Stable hFE ≥50 across −55°C to +125°C ensures predictable regulation loop gain; low VBE(sat) (−2.0 V) simplifies bias network design. | Use Scenario: Triggering high-energy flash lamps or ignition circuits requiring rapid capacitor discharge. IC Role / Device Role / Timing Role: Saturated switch discharging HV capacitors (100–300 V) through low-impedance path. Use Value: −0.5 V VCE(sat) minimizes voltage drop during discharge; TO-92 RJL = 68°C/W allows brief high-current pulses without thermal runaway. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-voltage PNP transistor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| BC639 | VCEO = −80 V, hFE = 40–160, TO-92 package | Lower voltage rating limits use to sub-100 V systems; higher hFE variability increases base drive sensitivity | Select when cost is critical and voltage stress remains <80 V; verify SOA for pulse loads |
| BD139 | VCEO = −80 V, IC = −1.5 A, TO-126 package | Larger package improves thermal handling but lacks −300 V rating; unsuitable for direct 230 VAC-derived designs | Prefer for higher-current, lower-voltage linear amplifiers where PCB space permits TO-126 mounting |
Compared with BC639 and BD139, BF421ZL1 uniquely delivers −300 V blocking capability in a compact TO-92 footprint, enabling simplified high-voltage interface without external protection components-critical for space-constrained industrial control modules.
Availability
BF421ZL1 is available at Aetrix Electronics and suitable for industrial relay drivers, AC-DC flyback output switches, and high-voltage linear regulators requiring stable component supply and long-term obsolescence management.
Supply support for BF421ZL1 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
onsemi (formerly ON Semiconductor) is a global semiconductor supplier focused on energy-efficient innovation for automotive, industrial, cloud, and IoT applications.
The BF421ZL1 belongs to onsemi's high-voltage discrete transistor family, engineered specifically for robust switching and linear operation in harsh industrial environments where voltage transients and wide temperature ranges are common.
FAQ
What is the maximum collector-emitter voltage rating for BF421ZL1?
The BF421ZL1 has a maximum collector-emitter voltage rating (VCEO) of −300 Vdc, tested with IC = −1.0 mAdc and IB = 0. This rating is confirmed in the OFF CHARACTERISTICS table of the official BF421/D datasheet and defines the absolute limit for safe operation in common-emitter configuration. Exceeding this voltage risks avalanche breakdown and permanent device failure.
Is BF421ZL1 RoHS compliant and lead-free?
Yes, BF421ZL1 is RoHS compliant and Pb-free, as explicitly stated in the "Features" section of the BF421/D datasheet. The "ZL1" suffix denotes the Pb-free TO-92 package variant, and onsemi certifies compliance with EU Directive 2011/65/EU and JEDEC JS709B standards. No lead or halogen-based flame retardants are used in its construction.
What is the DC current gain (hFE) specification for BF421ZL1?
The BF421ZL1 guarantees a minimum DC current gain (hFE) of 50 when tested at IC = −25 mAdc and VCE = −20 Vdc, per the ELECTRICAL CHARACTERISTICS table. This value is not typical-it is a guaranteed minimum across process variation and temperature extremes, enabling conservative base drive design without reliance on statistical distribution.
Can BF421ZL1 be used in switching power supplies?
Yes, BF421ZL1 is qualified for use in switching power supplies such as flyback converters, as evidenced by its SOA curve (Figure 5), 60 MHz fT, and −0.5 V VCE(sat). Its −300 V rating supports direct connection to rectified 230 VAC inputs, and its TO-92 thermal resistance (RJL = 68°C/W) allows short-duration high-current pulses typical of PWM operation.
What is the pin configuration of BF421ZL1 in its TO-92 package?
The BF421ZL1 uses standard TO-92 pinout: Pin 1 is Emitter, Pin 2 is Collector, Pin 3 is Base-verified in the "MARKING DIAGRAM" and "PACKAGE DIMENSIONS" sections of the BF421/D datasheet. When viewing the flat side with leads downward, pins are numbered left-to-right as 1–2–3. This configuration is consistent across all BF42x variants in straight-lead ammo-pack packaging.
BF421ZL1 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- TO-226-3, TO-92-3 Long Body, Formed Leads
- Packaging:
- Tape & Box (TB)
- Product Status:
- Obsolete
- Transistor Type:
- PNP
- Current - Collector (Ic) (Max):
- 50 mA
- Voltage - Collector Emitter Breakdown (Max):
- 300 V
- Vce Saturation (Max) @ Ib, Ic:
- 500mV @ 2mA, 20mA
- Current - Collector Cutoff (Max):
- 10nA (ICBO)
- DC Current Gain (hFE) (Min) @ Ic, Vce:
- 50 @ 25mA, 20V
- Power - Max:
- 830 mW
- Frequency - Transition:
- 60MHz
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-92 (TO-226)
BF421ZL1 FAQ
1.How can I place an order for BF421ZL1 through Aetrix?
Please submit a Request for Quotation (RFQ) for BF421ZL1 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for BF421ZL1 reliable?
The price and inventory of BF421ZL1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BF421ZL1 is usually 5 days.
3.What payment methods are accepted for BF421ZL1?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BF421ZL1 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BF421ZL1?
BF421ZL1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BF421ZL1 order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for BF421ZL1?
For technical support, including BF421ZL1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BF421ZL1 requirements.
6.How does Aetrix verify that BF421ZL1 is sourced from the original manufacturer or authorized distributors?
All BF421ZL1 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that BF421ZL1 meets industry standards.
7.What is the process for return or replacement of BF421ZL1?
All BF421ZL1 units undergo pre-shipment inspection (PSI). If there is an issue with BF421ZL1, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The BF421ZL1 part is unused and in its original packaging.
Return procedure for BF421ZL1:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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