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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

onsemi BF422

Name: BF422
Brand: onsemi
SKU: BF422
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BF422

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-226-3, TO-92-3 Long Body

Datasheet:: BF422.pdf

Description:: TRANS NPN 250V 0.05A TO92

Quantity:: RFQ Add To RFQ list

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Inventory:7,296

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Product details

Overview

BF422 from onsemi is an NPN silicon high-voltage transistor in TO-92 package, rated for 250 V_CEO, 250 V_CBO, 5.0 V_EBO, 50 mA continuous collector current, and 830 mW power dissipation at 25°C - designed for high-voltage switching and amplifier stages in CRT deflection, relay drivers, and pulse generators.

For engineers reviewing the BF422 datasheet, pinout, applications, or equivalent options, key selection criteria include verified V_CEO/V_CBO ratings, h_FE ≥50 at 25 mA/20 V, f_T = 60 MHz, C_re = 1.6 pF, and thermal resistance R_JA = 150 °C/W under standard FR4 mounting conditions.

Technical Context

The BF422 operates as a general-purpose NPN bipolar junction transistor optimized for high-voltage linear and switching applications where breakdown voltage and moderate gain stability are critical. Its 250 V rating enables use in flyback snubbers and horizontal deflection circuits without cascading devices.

It features a fixed three-terminal structure (Emitter–Collector–Base), with DC current gain h_FE specified at 50 (min) under 25 mA I_C and 20 V V_CE, and saturation voltages V_CE(sat) ≤ 0.5 V and V_BE(sat) ≤ 2.0 V at I_C/I_B = 10 - confirming suitability for low-loss switching with modest base drive.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	250 Vdc - supports operation in 200 V-class supply rails with margin for transient spikes
V_CBO	250 Vdc - ensures safe collector-base reverse bias in high-side switch configurations
I_C (continuous)	50 mAdc - defines maximum steady-state load current before thermal derating applies
h_FE	≥50 at I_C = 25 mA, V_CE = 20 V - provides predictable base drive requirements for saturated switching
f_T	60 MHz - enables stable amplification up to mid-VHF range in tuned RF stages
C_re	1.6 pF at V_CB = 30 V - limits Miller feedback in high-speed switching, reducing turn-off delay
R_JA	150 °C/W - requires heatsinking or layout copper for sustained >300 mW dissipation

Pinout & Package

Package: TO-92 (Case 29, Style 14), through-hole, Pb-free option available (BF422ZL1G). Standard lead form with 0.1" pitch, 5 mm lead length, and 200 mm² 1 oz copper pad per JEDEC mounting condition.

Pin/Terminal	Circuit Role	Design Meaning
1	Emitter	Reference terminal for current flow; connected to ground or low-side return path in common-emitter configuration
2	Collector	High-voltage output node; handles full V_CEO stress and carries load current
3	Base	Control input; requires ~2.0 V forward bias and ~2 mA drive for full saturation at 20 mA I_C

Key Features

Feature	Design Value
High V_CEO/V_CBO	250 V rating enables direct interface with 170–200 VDC bus lines in CRT and industrial power supplies
Stable h_FE over temperature	h_FE maintained across −55°C to +125°C per Figure 4, supporting reliable gain in wide-temperature environments
Low C_re	1.6 pF minimizes capacitive coupling between collector and base, improving switching speed and stability in high-gain stages
Pb-free packaging	BF422ZL1G variant complies with RoHS Directive 2011/65/EU and JEDEC J-STD-020 moisture sensitivity level 1

Applications

Horizontal Deflection Circuits	Relay Drivers
Use Scenario: Horizontal output stage in CRT-based oscilloscopes and legacy monitors requiring fast switching at 15.625 kHz with 200–250 V swing. IC Role / Device Role / Timing Role: NPN switching transistor operating in common-emitter mode with active clamp and snubber network. Use Value: 250 V_CEO withstands flyback voltage peaks; 60 MHz f_T ensures clean edge fidelity at line frequency.	Use Scenario: Solid-state replacement for electromechanical relays controlling 24–48 VDC industrial loads up to 50 mA. IC Role / Device Role / Timing Role: Low-power, high-voltage switch interfacing microcontroller GPIO to inductive coil. Use Value: V_CE(sat) ≤ 0.5 V reduces coil power loss; 150 °C/W R_JA allows operation on standard PCB without heatsink.
Pulse Generators	High-Voltage Amplifier Stages
Use Scenario: Monostable multivibrator and pulse shaper in test equipment generating <100 ns rise-time pulses into 50 Ω loads. IC Role / Device Role / Timing Role: Fast-switching NPN used in emitter-follower or grounded-base topology for pulse sharpening. Use Value: 1.6 pF C_re and 60 MHz f_T jointly support sub-10 ns propagation delay in optimized layouts.	Use Scenario: First-stage preamplifier in photomultiplier tube (PMT) signal conditioning chains handling 100–200 V bias rails. IC Role / Device Role / Timing Role: High-input-impedance common-emitter amplifier with active load or resistive collector termination. Use Value: 250 V_CBO isolates base from high-voltage collector node; h_FE ≥50 ensures ≥10 dB small-signal gain at 1 MHz.

Horizontal Deflection Circuits

Relay Drivers

Use Scenario: Horizontal output stage in CRT-based oscilloscopes and legacy monitors requiring fast switching at 15.625 kHz with 200–250 V swing.

IC Role / Device Role / Timing Role: NPN switching transistor operating in common-emitter mode with active clamp and snubber network.

Use Value: 250 V_CEO withstands flyback voltage peaks; 60 MHz f_T ensures clean edge fidelity at line frequency.

Use Scenario: Solid-state replacement for electromechanical relays controlling 24–48 VDC industrial loads up to 50 mA.

IC Role / Device Role / Timing Role: Low-power, high-voltage switch interfacing microcontroller GPIO to inductive coil.

Use Value: V_CE(sat) ≤ 0.5 V reduces coil power loss; 150 °C/W R_JA allows operation on standard PCB without heatsink.

Pulse Generators

High-Voltage Amplifier Stages

Use Scenario: Monostable multivibrator and pulse shaper in test equipment generating <100 ns rise-time pulses into 50 Ω loads.

IC Role / Device Role / Timing Role: Fast-switching NPN used in emitter-follower or grounded-base topology for pulse sharpening.

Use Value: 1.6 pF C_re and 60 MHz f_T jointly support sub-10 ns propagation delay in optimized layouts.

Use Scenario: First-stage preamplifier in photomultiplier tube (PMT) signal conditioning chains handling 100–200 V bias rails.

IC Role / Device Role / Timing Role: High-input-impedance common-emitter amplifier with active load or resistive collector termination.

Use Value: 250 V_CBO isolates base from high-voltage collector node; h_FE ≥50 ensures ≥10 dB small-signal gain at 1 MHz.

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage NPN transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BF420	Higher V_CEO/V_CBO (300 V), same h_FE, identical TO-92 package and pinout	Suitable where 300 V margin is required (e.g., 250 V bus with >50 V transients)	Select BF420 when system-level surge testing exceeds 250 V or when design reuse across BF420/BF422 platforms is needed
MPSA42	Same V_CEO = 300 V, higher I_C = 500 mA, larger TO-92 variant (Case 29-10), different pinout (E-B-C vs E-C-B)	Used in higher-current HV switching (e.g., neon sign drivers); not pin-compatible	Choose MPSA42 only if board layout accommodates revised pinout and thermal mass supports 625 mW dissipation

Compared with BF422, BF420 offers higher voltage headroom without layout change, while MPSA42 delivers greater current capacity but requires PCB revision due to reversed base/collector pins and larger thermal footprint.

Availability

BF422 is available at Aetrix Electronics and suitable for horizontal deflection circuits, relay drivers, pulse generators, and high-voltage amplifier stages requiring stable component supply with RoHS-compliant packaging options including BF422ZL1G.

Supply support for BF422 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 delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The BF422 belongs to onsemi's high-voltage discrete transistor family, engineered specifically for reliability-critical analog and switching functions in legacy display systems, industrial controls, and instrumentation where voltage robustness and parameter consistency are prioritized over ultra-high speed.

FAQ

What is the maximum collector-emitter voltage rating for BF422?

The BF422 has a guaranteed minimum V_CEO rating of 250 Vdc under test condition I_C = 1.0 mAdc and I_B = 0. This rating is validated per onsemi's BF420/D datasheet Rev. 4 and applies to the BF422ZL1G variant. Operation above this voltage risks avalanche breakdown and permanent degradation of the BF422 junction integrity.

Is BF422 pin-compatible with BF420?

Yes, BF422 is fully pin-compatible with BF420: both use TO-92 package (Style 14) with identical pin 1 (Emitter), pin 2 (Collector), pin 3 (Base) assignment and mechanical dimensions. The BF422 and BF420 share identical footprint, soldering profile, and mounting requirements - enabling drop-in substitution where 250 V rating suffices.

What is the typical DC current gain (hFE) of BF422 at operating conditions?

The BF422 specifies h_FE ≥ 50 at I_C = 25 mAdc and V_CE = 20 Vdc per the official onsemi BF420/D datasheet. Measured values typically range from 50 to 120 depending on batch and junction temperature; design margins should assume the minimum 50 value for worst-case base drive calculation in the BF422 circuit.

Does BF422 support Pb-free assembly processes?

Yes, the BF422ZL1G variant is explicitly designated as Pb-free and complies with RoHS Directive 2011/65/EU. It uses matte tin lead finish and meets JEDEC J-STD-020 moisture sensitivity level 1, allowing standard reflow profiles without pre-bake for the BF422ZL1G part number.

What thermal resistance does BF422 exhibit under standard PCB mounting?

When mounted on a FR4 board with 200 mm² of 1 oz copper and 5 mm lead length (per Note 1 in the BF420/D datasheet), the BF422 exhibits R_JA = 150 °C/W. This value governs junction-to-ambient temperature rise during continuous operation and must be applied to calculate maximum allowable power dissipation at elevated ambient temperatures for the BF422.

BF422 Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-226-3, TO-92-3 Long Body

Packaging:: Bulk

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 50 mA

Voltage - Collector Emitter Breakdown (Max):: 250 V

Vce Saturation (Max) @ Ib, Ic:: 500mV @ 2mA, 20mA

Current - Collector Cutoff (Max):: -

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)

BF422 FAQ

1.How can I place an order for BF422 through Aetrix?

Please submit a Request for Quotation (RFQ) for BF422 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 BF422 reliable?

The price and inventory of BF422 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BF422 is usually 5 days.

3.What payment methods are accepted for BF422?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BF422 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BF422?

BF422 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BF422 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 BF422?

For technical support, including BF422 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BF422 requirements.

6.How does Aetrix verify that BF422 is sourced from the original manufacturer or authorized distributors?

All BF422 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 BF422 meets industry standards.

7.What is the process for return or replacement of BF422?

All BF422 units undergo pre-shipment inspection (PSI). If there is an issue with BF422, 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 BF422 part is unused and in its original packaging.

Return procedure for BF422:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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