onsemi PN4249

Overview

PN4249 from Fairchild Semiconductor is a PNP general-purpose bipolar junction transistor (BJT) designed for amplification and switching in low-to-medium power circuits, with V_CEO = 60 V, I_C = 500 mA continuous, h_FE = 100–300 at I_C = 100 µA, and TO-92 package. It serves as a discrete signal amplifier or saturated switch in consumer power supplies, LED drivers, and logic-level interface circuits.

For engineers reviewing the PN4249 datasheet, pinout, applications, or equivalent options, key selection considerations include its PNP polarity, 60 V breakdown rating, 500 mA collector current capability, thermal resistance (R_θJA = 200 °C/W), and suitability for DC-coupled small-signal amplification or low-speed switching up to ~100 kHz.

Technical Context

The PN4249 operates as a silicon PNP BJT fabricated on Fairchild's Process 68, optimized for general-purpose linear amplification and saturated switching. Its DC current gain (h_FE) is specified from 100 to 300 at V_CE = 5.0 V and I_C = 100 µA, and it achieves V_CE(sat) ≤ 0.25 V at I_C = 10 mA / I_B = 0.5 mA - confirming robust low-loss switching behavior.

Small-signal parameters include input impedance (h_ie) of 2.5–17 kΩ, output admittance (h_oe) of 5–40 µmhos, and noise figure of 3.0 dB at 1 kHz with 250 µA bias - indicating suitability for audio preamplifier stages and low-noise sensor interface applications where moderate gain and bandwidth are required.

Key Specifications

Pinout & Package

PN4249 is housed in a standard through-hole TO-92 plastic package with straight leads and no lead clip. Pin identification follows JEDEC TO-92 orientation: flat side facing viewer, leads down, left-to-right = Emitter (E), Base (B), Collector (C).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP general-purpose amplifier applications.

Compared with BC557 and MPSA92, PN4249 delivers optimal balance of 60 V breakdown, 500 mA current, and 100–300 h_FE for mid-range industrial control and audio interface designs - offering higher voltage headroom than BC557 and tighter gain consistency than MPSA92 without over-engineering.

Availability

PN4249 is available at Aetrix Electronics and suitable for industrial control panels, LED lighting subsystems, and audio signal conditioning circuits requiring stable component supply and long-term obsolescence management.

Supply support for PN4249 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 devices before its acquisition by ON Semiconductor in 2016.

PN4249 belongs to Fairchild's general-purpose bipolar transistor product line, engineered for cost-effective, reliable amplification and switching in consumer, industrial, and automotive-qualified auxiliary circuits.

FAQ

What is the maximum continuous collector current rating for PN4249?

The PN4249 has a maximum continuous collector current (I_C) rating of 500 mA at T_A = 25°C. This rating assumes proper PCB copper area or heatsinking to maintain junction temperature below 150°C. Derating is required above 25°C ambient - 5.0 mW/°C - meaning usable current drops to ~375 mA at 50°C ambient without additional cooling. The PN4249 datasheet specifies this limit under steady-state DC conditions.

Is PN4249 suitable for audio amplifier applications?

Yes, PN4249 is suitable for low-frequency audio amplifier stages such as microphone preamplifiers or tone-control buffers. Its 3.0 dB noise figure at 1 kHz, h_ie of 2.5–17 kΩ, and h_FE of 100–300 support stable gain and low added noise. However, it is not intended for high-fidelity power output stages due to limited bandwidth and thermal constraints. For best results, bias the PN4249 in Class-A with emitter degeneration and adequate decoupling.

What is the pin configuration of PN4249 in the TO-92 package?

The PN4249 uses standard JEDEC TO-92 pinout: with the flat side facing the viewer and leads pointing downward, the left-to-right pin order is Emitter (E), Base (B), Collector (C). This matches Fairchild's documented orientation for PKG 92 devices. The "first wire off" is the emitter in standard ammo packaging, and the flat surface aligns with the emitter pin - critical for correct PCB footprint layout and assembly verification.

Does PN4249 have a lead-free or RoHS-compliant version?

The original PN4249 datasheet predates mandatory RoHS compliance and does not specify lead-free construction. However, ON Semiconductor (which acquired Fairchild) offers RoHS-compliant equivalents such as the NSS60200LT1G, which shares similar PNP characteristics but in SOT-23. For legacy PN4249, Aetrix Electronics sources only historically compliant batches verified against JESD22-A112 and JEDEC J-STD-020 moisture sensitivity standards - consult lot-specific CoC for halogen content and Pb concentration.

How does PN4249 compare to PN2222 in terms of polarity and application?

PN4249 is a PNP transistor, while PN2222 is an NPN device - they are complementary but not interchangeable without circuit redesign. PN4249 sinks current from V_CC to load (high-side switch), whereas PN2222 sources current from load to ground (low-side switch). Their absolute maximum ratings differ: PN4249 has V_CEO = 60 V and I_C = 500 mA; PN2222 has V_CEO = 40 V and I_C = 800 mA. Use PN4249 where inverted logic or high-side control is required; do not substitute directly into NPN-based schematics.