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NXP Semiconductors BF421,112
- Part No.:
- BF421,112
- Manufacturer:
- NXP Semiconductors
- Category:
- Single Bipolar Transistors
- Package:
- TO-226-3, TO-92-3 (TO-226AA) Formed Leads
- Datasheet:
-
BF421,112.pdf
- Description:
- TRANS PNP 300V 0.05A TO-92-3
- Quantity:
- Payment:
- Shipping:
Inventory:6,848
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Product details
Overview
BF421,112 from NXP Semiconductors (formerly Philips) is a PNP high-voltage transistor in TO-92 (SOT54/SC-43A) package, rated for −300 V collector-base and collector-emitter voltage, 830 mW power dissipation, 1.6 pF feedback capacitance, and 60 MHz transition frequency. It serves in class-B video output stages of colour television and professional monitor equipment.
For engineers reviewing the BF421,112 datasheet, BF421,112 pinout, BF421,112 application, or BF421,112 equivalent, key selection criteria include high-voltage PNP switching capability, low feedback capacitance for video bandwidth preservation, DC current gain ≥50 at −25 mA, and thermal resistance of 150 K/W under PCB-mounted conditions.
Technical Context
The BF421,112 operates as a high-voltage PNP bipolar junction transistor optimized for linear amplification in video output stages. Its −300 V VCBO and VCEO ratings enable safe operation in high-swing CRT deflection and anode drive circuits, while its 1.6 pF Cre minimizes signal phase shift and instability at RF/video frequencies.
Designed for through-hole mounting on printed-circuit boards, it delivers stable hFE ≥50 at −20 V VCE and −25 mA IC, with VCEsat ≤ −0.6 V at −30 mA IC / −5 mA IB. Its fT of 60 MHz supports bandwidth-critical analog video signal handling without gain roll-off.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCBO | −300 V - supports high-voltage biasing in CRT anode supply and deflection circuits without breakdown |
| VCEO | −300 V - enables full swing collector-emitter operation in class-B video output stages |
| Cre | 1.6 pF - reduces Miller effect and maintains video bandwidth up to ~60 MHz |
| fT | 60 MHz - ensures sufficient small-signal gain at video frequencies including horizontal sync components |
| Ptot | 830 mW - provides thermal headroom for continuous video output duty cycles at Tamb ≤ 25 °C |
| hFE | ≥50 - guarantees reliable current amplification in linear video driver configurations |
| Rth(j-a) | 150 K/W - defines junction-to-ambient thermal rise under standard PCB mounting per note 1 |
Pinout & Package
Package: TO-92 plastic single-ended leaded (through-hole), SOT54 / SC-43A, 3-lead, dimensions per IEC 60134 outline (L = 14.5 mm, D = 4.8 mm, E = 4.2 mm, e = 2.54 mm).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Base | Current-controlled input node; requires −5 mA base drive for −30 mA collector saturation |
| 2 | Collector | High-voltage output terminal; connected to CRT anode or deflection yoke return path |
| 3 | Emitter | Common reference node; tied to regulated negative rail or ground in class-B configuration |
Key Features
| Feature | Design Value |
|---|---|
| Low feedback capacitance | 1.6 pF Cre - preserves video signal integrity and prevents oscillation in wideband amplifier designs |
| High collector-base voltage rating | −300 V VCBO - enables direct use in CRT horizontal output and EHT generator stages |
| Stable DC current gain | hFE ≥50 at −20 V VCE / −25 mA IC - ensures predictable biasing and linearity in analog video drivers |
| Thermally characterized mounting | Rth(j-a) = 150 K/W on PCB - allows accurate junction temperature estimation for reliability analysis |
Applications
| Colour Television Video Output | Professional Monitor Deflection |
|---|---|
Use Scenario: Driving CRT anode and deflection yoke in broadcast-grade colour TV receivers. IC Role / Device Role / Timing Role: PNP high-voltage linear amplifier in class-B video output stage. Use Value: −300 V VCEO withstands flyback-induced voltage spikes; 1.6 pF Cre maintains luminance/chrominance separation. | Use Scenario: Horizontal and vertical deflection circuitry in medical and studio-grade monitors. IC Role / Device Role / Timing Role: High-voltage PNP switch/amplifier in synchronized deflection waveform generation. Use Value: 60 MHz fT supports precise timing of 15.734 kHz horizontal and 60 Hz vertical sync signals without phase lag. |
| Video Signal Amplification | High-Voltage Bias Regulation |
Use Scenario: Final-stage amplification of composite video signals prior to CRT grid modulation. IC Role / Device Role / Timing Role: Linear PNP emitter-follower buffer with low output impedance. Use Value: hFE ≥50 ensures minimal loading on preceding video processing ICs; −0.6 V VCEsat limits signal distortion. | Use Scenario: Regulated high-voltage bias supply for CRT focus and screen grids. IC Role / Device Role / Timing Role: Series pass element in discrete high-voltage linear regulator. Use Value: −300 V VCBO accommodates >250 V regulated outputs; 830 mW Ptot handles steady-state dissipation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar PNP high-voltage transistor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| BF423,112 | −250 V VCBO/VCEO (vs. −300 V); otherwise identical pinout, Cre, fT, and package | Lower voltage margin restricts use in >250 V CRT anode circuits | Select BF423,112 only where system peak voltages remain ≤250 V |
| BC639-16 | −80 V VCEO; higher hFE (100–250); same TO-92 package but lower voltage rating | Not suitable for CRT anode or deflection; limited to low-voltage video preamp stages | Use BC639-16 only in sub-80 V signal chain positions requiring higher gain |
Compared with BF423,112 and BC639-16, the BF421,112 uniquely delivers −300 V blocking capability with 1.6 pF Cre and 60 MHz fT in TO-92 - making it irreplaceable in legacy CRT video output stages demanding both high voltage and video bandwidth.
Availability
BF421,112 is available at Aetrix Electronics and suitable for colour television repair, professional monitor refurbishment, and legacy video equipment maintenance requiring stable component supply and long-term obsolescence support.
Supply support for BF421,112 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
NXP Semiconductors is a global semiconductor company formed from the spin-off of Philips Semiconductors in 2006, specializing in high-reliability analog, logic, and RF components.
The BF421,112 belongs to NXP's legacy discrete transistor portfolio designed specifically for high-voltage analog video applications in CRT-based consumer and professional display systems.
FAQ
What is the maximum collector-emitter voltage rating for BF421,112?
The BF421,112 has a maximum collector-emitter voltage (VCEO) rating of −300 V under open-base conditions. This rating is confirmed in the Philips 2004 datasheet limiting values table and applies to continuous DC operation. Exceeding this voltage risks permanent junction breakdown. The BF421,112 must be used within this limit in CRT anode and deflection circuits where transient spikes may approach this threshold.
Is BF421,112 pin-compatible with BF423,112?
Yes, BF421,112 is pin-compatible with BF423,112 - both use identical TO-92 (SOT54) packaging and share the same pin 1 (base), pin 2 (collector), pin 3 (emitter) assignment. However, BF423,112 has lower −250 V VCBO/VCEO ratings, so substitution requires verification that system peak voltages remain within that limit. The BF421,112 remains the only option when −300 V capability is mandatory.
What is the typical feedback capacitance (Cre) of BF421,112 and why does it matter?
The BF421,112 has a maximum feedback capacitance (Cre) of 1.6 pF at −30 V VCE and 1 MHz. This low value minimizes Miller multiplication in high-gain video amplifiers, preserving bandwidth and preventing instability. In CRT video output stages, maintaining Cre ≤1.6 pF ensures luminance/chrominance signal fidelity and avoids high-frequency oscillation - a critical requirement confirmed in the original Philips specification.
Can BF421,112 be used in surface-mount designs?
No, BF421,112 is not suitable for surface-mount designs. It is exclusively packaged in the through-hole TO-92 (SOT54/SC-43A) format with 2.54 mm lead pitch. No SMD variant was released by Philips/NXP. Any attempt to mount BF421,112 on SMT pads would compromise mechanical reliability and thermal performance. For SMT alternatives, engineers must select functionally distinct devices such as SOT-23 PNP transistors with lower voltage ratings.
What is the DC current gain (hFE) range for BF421,112 and under what conditions is it specified?
The BF421,112 has a minimum DC current gain (hFE) of 50, specified at VCE = −20 V and IC = −25 mA, per the Philips 2004 datasheet characteristics table. No maximum hFE is given. This gain level ensures predictable biasing in class-B video output stages. Gain drops significantly outside these conditions - for example, at IC < −5 mA or VCE > −10 V - so design margins must account for this dependency. The BF421,112 performs reliably only within its documented hFE test envelope.
BF421,112 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- NXP Semiconductors
- Series:
- -
- Package/Case:
- TO-226-3, TO-92-3 (TO-226AA) Formed Leads
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Transistor Type:
- PNP
- Current - Collector (Ic) (Max):
- 50 mA
- Voltage - Collector Emitter Breakdown (Max):
- 300 V
- Vce Saturation (Max) @ Ib, Ic:
- 600mV @ 5mA, 30mA
- 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:
- 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-92-3
BF421,112 FAQ
1.How can I place an order for BF421,112 through Aetrix?
Please submit a Request for Quotation (RFQ) for BF421,112 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 BF421,112 reliable?
The price and inventory of BF421,112 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BF421,112 is usually 5 days.
3.What payment methods are accepted for BF421,112?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BF421,112 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BF421,112?
BF421,112 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BF421,112 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 BF421,112?
For technical support, including BF421,112 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BF421,112 requirements.
6.How does Aetrix verify that BF421,112 is sourced from the original manufacturer or authorized distributors?
All BF421,112 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 BF421,112 meets industry standards.
7.What is the process for return or replacement of BF421,112?
All BF421,112 units undergo pre-shipment inspection (PSI). If there is an issue with BF421,112, 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 BF421,112 part is unused and in its original packaging.
Return procedure for BF421,112:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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