onsemi 2N5306

Overview

2N5306 from Fairchild Semiconductor is an NPN Darlington transistor in TO-92 package, designed for high-current-switching applications with DC current gain (hFE) of 7,000–70,000 at IC = 2.0mA to 100mA, VCE = 5.0V, and maximum continuous collector current of 1.2A. It operates across –55°C to +150°C and supports low-saturation switching in relay drivers and power interface circuits.

For engineers reviewing the 2N5306 datasheet, pinout, applications, or equivalent options, key selection considerations include its Darlington architecture enabling ultra-high hFE at moderate currents, VCE(sat) = 1.4V at IC = 200mA/IB = 0.2mA, and thermal resistance RθJA = 200°C/W - critical for thermally constrained PCB layouts and discrete power control stages.

Technical Context

The 2N5306 implements a monolithic NPN Darlington pair with integrated base-emitter resistor network absent - requiring external base drive control. Its high hFE enables microampere-level base current to switch >1A collector loads, while V(BR)CEO = 25V and V(BR)CBO = 25V define safe operating voltage limits under open-base conditions.

Thermal design is constrained by RθJA = 200°C/W and PD = 625mW at TA = 25°C, derating linearly at 5.0mW/°C above ambient. Small-signal hfe drops from 7,000 at 1kHz to 6.0 at 10MHz, confirming its optimization for DC/low-frequency switching rather than RF amplification.

Key Specifications

Pinout & Package

2N5306 is housed in a standard TO-92 plastic package with 3 leads. Pin identification follows JEDEC TO-92 outline: lead 1 = Emitter, lead 2 = Collector, lead 3 = Base - verified per Fairchild Rev. B1 datasheet diagram and dimensioned mechanical drawing.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Darlington transistor applications.

Compared with MPSA14 and ULN2003A, the 2N5306 delivers superior continuous current handling (1.2A vs. 0.5A/channel), wider hFE tolerance for production consistency, and standalone flexibility for custom base-drive design - making it optimal for single-load, thermally managed, high-reliability switching nodes.

Availability

2N5306 is available at Aetrix Electronics and suitable for relay driver circuits, DC motor on/off control, solenoid actuation interfaces, and industrial PLC output modules requiring stable component supply and long-term obsolescence management.

Supply support for 2N5306 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The 2N5306 belongs to Fairchild's legacy bipolar transistor family engineered for high-gain, medium-power discrete switching - targeting cost-sensitive industrial controls and electromechanical interface applications where reliability and thermal robustness are essential.

FAQ

What is the maximum continuous collector current rating for the 2N5306?

The 2N5306 has a maximum continuous collector current (IC) rating of 1.2 A at TA = 25°C, as specified in the Absolute Maximum Ratings table. This rating assumes adequate PCB copper area and ambient airflow; derating is required above 25°C per the 5.0 mW/°C thermal specification. The 2N5306 must not be operated beyond this limit in sustained DC or high-duty-cycle pulse conditions without thermal analysis.

Does the 2N5306 include built-in base resistors or protection diodes?

No, the 2N5306 is a bare Darlington transistor without integrated base resistors or clamp diodes. External base current limiting and flyback suppression (e.g., freewheeling diode across inductive loads) must be implemented in the circuit. This distinguishes it from array devices like ULN2003A and gives designers full control over drive characteristics - a key feature of the 2N5306 in precision switching applications.

What is the typical VCE(sat) of the 2N5306 under standard test conditions?

The 2N5306 exhibits a typical VCE(sat) of 1.4 V when tested at IC = 200 mA and IB = 0.2 mA, per the On Characteristics table. This value reflects the saturated voltage drop across the Darlington pair during full conduction and directly impacts power dissipation (P = IC × VCE(sat)). Designers should verify saturation under actual operating conditions, as VCE(sat) increases with temperature and decreases slightly at higher IB/IC ratios.

Can the 2N5306 replace the MPSA14 in existing designs?

The 2N5306 can replace the MPSA14 in many TO-92-based designs due to identical pinout (Emitter–Collector–Base), same package, and overlapping hFE range - but only if the application requires ≥1.2A current or benefits from lower VCE(sat). Because the 2N5306 has higher power dissipation (625 mW vs. 625 mW for MPSA14, but different thermal profiles), layout review is recommended. The 2N5306 is not a guaranteed drop-in substitute without validation.

What is the junction-to-ambient thermal resistance (RθJA) of the 2N5306?

The junction-to-ambient thermal resistance (RθJA) of the 2N5306 is 200°C/W, measured under standard JEDEC test conditions on FR-4 PCB with minimum copper. This value determines how much the junction temperature rises above ambient per watt of dissipated power. For example, at 300 mW dissipation, TJ rises ~60°C above TA - so ambient must stay below +90°C to remain within the +150°C max TJ limit. The 2N5306's RθJA confirms its suitability for natural-convection-only applications with conservative power budgets.