onsemi PN3643_D26Z

Overview

PN3643_D26Z from Fairchild Semiconductor is an NPN general-purpose bipolar junction transistor (BJT) designed for amplification and switching in low-to-medium power circuits, with V_CEO = 30 V, I_C = 500 mA continuous, h_FE = 100–300 at I_C = 150 mA, and TO-92 package. It operates across –55 °C to +150 °C and is used in signal amplification stages of consumer audio preamps and discrete logic-level switching in industrial control I/O modules.

For engineers reviewing the PN3643_D26Z datasheet, pinout, applications, or equivalent options, key selection considerations include its DC current gain range, V_CE(sat) ≤ 0.22 V at I_C = 150 mA/I_B = 15 mA, thermal resistance R_θJA = 200 °C/W, and suitability for linear amplification up to 30 MHz.

Technical Context

The PN3643_D26Z is a silicon NPN BJT optimized for general-purpose analog amplification and saturated switching. Its h_FE variation (100–300) supports consistent biasing across production lots, while V_CE(sat) = 0.22 V enables low-loss switching in 5 V–12 V logic interface circuits. Cob = 8.0 pF and f_T ≈ 100 MHz (via h_fe = 2.5 at 100 MHz) confirm usability in RF-coupled IF stages up to 30 MHz.

Thermal design relies on R_θJA = 200 °C/W and P_D = 625 mW at 25 °C, derating 5.0 mW/°C above ambient. The device meets JEDEC TO-92 mechanical standards with defined lead spacing (1.27 mm pitch), enabling compatibility with standard through-hole PCB footprints and wave-solder processes.

Key Specifications

Pinout & Package

PN3643_D26Z is housed in a standard JEDEC TO-92 plastic package with 3 leads, compatible with automated insertion and wave soldering. Dimensions conform to Fairchild's published outline: body height 4.58 mm max, lead pitch 1.27 mm, and lead diameter 0.38 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC547B and MPSA18, PN3643_D26Z delivers optimal balance of current drive (500 mA), moderate voltage rating (30 V), and wide h_FE tolerance-making it ideal for cost-sensitive, medium-power discrete amplifier and switch designs where thermal headroom and manufacturability are prioritized.

Availability

PN3643_D26Z is available at Aetrix Electronics and suitable for industrial motor control, consumer audio signal conditioning, and programmable logic I/O interfacing requiring stable component supply and long-term obsolescence management.

Supply support for PN3643_D26Z 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 manufacturer specializing in power management, analog, and discrete devices before its acquisition by ON Semiconductor in 2016.

PN3643_D26Z belongs to Fairchild's legacy general-purpose BJT product line, engineered for reliability and ease of use in cost-sensitive linear and switching applications across consumer, industrial, and computing markets.

FAQ

What is the maximum continuous collector current rating for PN3643_D26Z?

The PN3643_D26Z has a maximum continuous collector current (I_C) rating of 500 mA at T_A = 25 °C. This rating assumes proper PCB copper area and ambient airflow; derating is required above 25 °C per the 5.0 mW/°C thermal specification. At 65 °C ambient, the usable I_C drops to approximately 425 mA to maintain junction temperature ≤ 150 °C. The PN3643_D26Z datasheet confirms this value under "Electrical Characteristics" with test condition IC = 500 mA, continuous.

Does PN3643_D26Z support RF amplification up to 30 MHz?

Yes, PN3643_D26Z supports RF amplification up to 30 MHz, as validated by its G_pe = 10 dB and η = 60% at V_CE = 15 V, f = 30 MHz, with specified source and load impedances (R_G = 140 Ω, R_L = 260 Ω). Its h_fe = 2.5 at 100 MHz further indicates usable gain bandwidth. The PN3643_D26Z is not intended for >100 MHz operation but performs reliably in IF amplifier stages of AM/FM receivers and wireless sensor transceivers.

What is the pin configuration of PN3643_D26Z in the TO-92 package?

PN3643_D26Z uses the standard TO-92 pinout: Pin 1 is Emitter, Pin 2 is Base, and Pin 3 is Collector-viewed with flat side facing outward and leads pointing downward. This configuration is explicitly stated in the Fairchild PN3643 datasheet Rev. B and matches JEDEC TO-92 mechanical drawings. The PN3643_D26Z pinout enables direct substitution in legacy designs using identical footprint and orientation, including common-emitter amplifier and low-side switch topologies.

Can PN3643_D26Z replace BC547 in existing designs?

PN3643_D26Z can replace BC547 in many designs but requires verification of current and thermal requirements. While both share TO-92 packaging and NPN polarity, PN3643_D26Z supports 5× higher I_C (500 mA vs. 100 mA) and lower V_CE(sat) (0.22 V vs. ~0.6 V), making it suitable for higher-power loads. However, its h_FE range (100–300) differs from BC547B's (200–450), potentially affecting bias stability. Review the specific operating point before substituting PN3643_D26Z for BC547.

What is the thermal resistance from junction to ambient for PN3643_D26Z?

The thermal resistance from junction to ambient (R_θJA) for PN3643_D26Z is 200 °C/W, measured under standard JEDEC test conditions on FR-4 PCB with minimal copper. This value implies a 100 °C junction rise at 500 mW dissipation. For reliable operation near maximum ratings, designers should add thermal relief pads or increase copper area to reduce effective R_θJA. The PN3643_D26Z datasheet specifies this parameter in the "Thermal Characteristics" table under TA = 25 °C.