onsemi BF423ZL1

Overview

BF423ZL1 from onsemi is a PNP silicon high-voltage transistor rated for −250 V_CEO, −250 V_CBO, and −5.0 V_EBO, with continuous collector current of −500 mA, DC current gain (h_FE) ≥50 at −25 mA/−20 V, and saturation voltage V_CE(sat) ≤ −0.5 V at −20 mA/−2.0 mA drive - used in flyback snubber circuits, relay drivers, and HV switching stages in industrial power supplies.

For engineers reviewing the BF423ZL1 datasheet, pinout, applications, or equivalent options, key selection criteria include verified −250 V breakdown rating, TO-92 package thermal resistance (R_JA = 150 °C/W), low leakage (I_CBO ≤ −0.01 A), f_T = 60 MHz capability, and Pb-free RoHS-compliant construction per onsemi's BF421/D Rev. 5 specification.

Technical Context

This PNP bipolar junction transistor operates in linear or saturated switching modes with guaranteed V_CEO and V_CBO ratings of −250 V, enabling use in high-side switching and inductive load control where reverse-biased collector-base junction integrity is critical. Its f_T of 60 MHz supports moderate-speed switching up to ~10–20 MHz under specified bias conditions.

Thermal design relies on R_JL = 68 °C/W (junction-to-lead) and R_JA = 150 °C/W (junction-to-ambient on FR4 with 200 mm² copper), requiring careful PCB layout for sustained −500 mA operation. Cutoff leakage is tightly controlled: I_CBO ≤ −0.01 A at −200 V and I_EBO ≤ −100 nA at −5.0 V.

Key Specifications

Pinout & Package

BF423ZL1 is housed in a TO-92 (Case 29, Style 14) plastic package with straight leads and Pb-free finish. The device uses standard lead assignment: Pin 1 = Emitter, Pin 2 = Collector, Pin 3 = Base.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD2955G and BC639, BF423ZL1 uniquely balances TO-92 compactness, −250 V ruggedness, and predictable h_FE/V_CE(sat) - making it optimal for space-constrained, high-voltage industrial controls where neither higher-power nor lower-voltage alternatives meet all requirements.

Availability

BF423ZL1 is available at Aetrix Electronics and suitable for industrial relay drivers, flyback snubber circuits, and high-side load switches requiring stable component supply, long-term lifecycle support, and RoHS-compliant manufacturing.

Supply support for BF423ZL1 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 BF423ZL1 belongs to onsemi's high-voltage discrete transistor family, engineered specifically for ruggedized switching in industrial power conversion, protection circuitry, and HV interface stages.

FAQ

What is the maximum collector-emitter voltage rating for BF423ZL1?

The BF423ZL1 has a guaranteed V_CEO rating of −250 Vdc under test condition I_C = −1.0 mAdc and I_B = 0, as confirmed in the onsemi BF421/D Rev. 5 datasheet. This rating applies to common-emitter configuration and defines the absolute maximum reverse bias the device can withstand before breakdown. Exceeding this voltage risks irreversible avalanche failure. Derating is recommended for reliability in high-temperature or high-repetition applications.

Is BF423ZL1 pin-compatible with BF421ZL1?

Yes, BF423ZL1 is pin-compatible with BF421ZL1 - both share identical TO-92 package (Case 29, Style 14), same pinout (Pin 1 = Emitter, Pin 2 = Collector, Pin 3 = Base), and identical mechanical dimensions. However, BF421ZL1 is rated for −300 V_CEO/V_CBO, while BF423ZL1 is rated for −250 V. Substitution is acceptable only if system voltage remains within BF423ZL1's −250 V limit.

What is the typical DC current gain (h_FE) of BF423ZL1 at operating conditions?

The BF423ZL1 exhibits h_FE ≥50 when tested at I_C = −25 mAdc and V_CE = −20 Vdc per the onsemi BF421/D datasheet. This minimum value is guaranteed across temperature (−55°C to +150°C), with typical curves showing h_FE rising to ~100–120 at lower currents. Designers should verify gain stability under actual bias and thermal conditions, especially near maximum ratings.

Does BF423ZL1 support Pb-free soldering processes?

Yes, BF423ZL1 is explicitly marked as Pb-free, Halogen Free/BFR Free, and RoHS compliant per onsemi's documentation. It supports standard lead-free reflow profiles (e.g., J-STD-020D) with peak temperatures up to 260°C. The device uses matte tin lead finish and is qualified for both wave and reflow soldering - no special process modifications are required beyond standard Pb-free guidelines.

What is the thermal resistance from junction to ambient (R_JA) for BF423ZL1?

The BF423ZL1 has an R_JA of 150 °C/W when mounted on a FR4 PCB with 200 mm² of 1 oz copper and 5 mm lead length, as specified in the onsemi BF421/D datasheet. This value assumes natural convection cooling; actual R_JA improves with added copper area, thermal vias, or forced airflow. For sustained −500 mA operation, junction temperature must remain ≤+150°C - requiring ambient temperature derating per the 6.6 mW/°C slope above 25°C.