onsemi PN3645_D75Z

Overview

PN3645_D75Z from Fairchild Semiconductor is a PNP general-purpose bipolar junction transistor (BJT) designed for amplification and switching applications up to 500 mA collector current. It features V_CEO = 60 V, h_FE = 40–300 (at I_C = 0.1–300 mA), V_CE(sat) = 0.25–0.4 V, and TO-92 package with emitter-first lead orientation per D75Z taping specification. It is commonly used in low-voltage DC-DC converter bias circuits and discrete logic-level switching.

For engineers reviewing the PN3645_D75Z datasheet, pinout, applications, or equivalent options, key selection considerations include its PNP polarity, 60 V breakdown rating, thermal resistance of 200 °C/W (junction-to-ambient), saturation voltage behavior under 150 mA drive, and TO-92 mechanical compatibility with standard through-hole PCB footprints.

Technical Context

The PN3645_D75Z implements a silicon planar epitaxial PNP BJT structure fabricated on Process 63, optimized for stable DC gain and fast switching (t_on = 40 ns, t_off = 100 ns). Its base-emitter and collector-base junctions are rated for 5.0 V and 60 V respectively, supporting operation in grounded-emitter configurations with reverse-biased base control.

Thermal design relies on its R_θJA = 200 °C/W and R_θJC = 83.3 °C/W, with maximum power dissipation derated above 25°C at 5.0 mW/°C. The device operates across –55°C to +150°C junction temperature range, enabling use in industrial ambient environments without forced cooling at ≤300 mA continuous load.

Key Specifications

Pinout & Package

PN3645_D75Z is supplied in TO-92 plastic package with straight leads and no lead clip. Per D75Z taping specification, the first wire off the package is the collector, adhesive tape is on the top side, and the flat side of the transistor is oriented upward - critical for automated placement alignment.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPSA92 and PN2907A, PN3645_D75Z offers balanced trade-offs: lower V_CEO than MPSA92 but superior low-current h_FE stability versus PN2907A, making it optimal for mid-range industrial switching where 60 V rating and predictable 0.1–100 mA gain behavior are prioritized.

Availability

PN3645_D75Z is available at Aetrix Electronics and suitable for DC-DC converter bias circuits, discrete logic-level switching, industrial sensor interfaces, and legacy equipment repair requiring stable component supply and long-term obsolescence mitigation.

Supply support for PN3645_D75Z 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, acquired by ON Semiconductor in 2016. Its legacy products remain widely deployed in industrial and automotive systems.

The PN3645_D75Z belongs to Fairchild's general-purpose bipolar transistor product line, engineered for cost-effective amplification and switching in non-automotive industrial applications where robustness, thermal stability, and TO-92 footprint compatibility are essential.

FAQ

What is the pin configuration of PN3645_D75Z?

The PN3645_D75Z uses a TO-92 package with collector (C) as the first lead, emitter (E) as the last lead, and base (B) in the middle - matching standard PNP TO-92 orientation. This configuration is explicitly defined in the D75Z taping specification, where the flat side faces upward and adhesive tape is applied to the top surface. Always confirm orientation visually before soldering, as incorrect placement will reverse polarity functionality.

Does PN3645_D75Z support switching at 1 MHz?

The PN3645_D75Z has t_on = 40 ns and t_off = 100 ns, yielding a theoretical maximum toggle frequency near 3.5 MHz under ideal conditions. However, practical 1 MHz switching requires careful attention to base drive strength, load inductance, and layout parasitics - especially since V_CE(sat) rises above 0.4 V at I_C > 150 mA. For reliable 1 MHz operation, limit average I_C to ≤100 mA and use active base pull-down.

Is PN3645_D75Z RoHS compliant?

PN3645_D75Z was manufactured prior to full RoHS enforcement and does not carry formal RoHS certification. Its lead content exceeds EU Directive 2011/65/EU limits, and it is classified as non-RoHS under current compliance frameworks. For new designs requiring RoHS compliance, consider ON Semiconductor's NSS60201MR6T1G or similar qualified replacements with documented exemption status.

How does PN3645_D75Z compare to PN2907A in terms of thermal performance?

PN3645_D75Z and PN2907A share identical thermal characteristics: R_θJA = 200 °C/W and R_θJC = 83.3 °C/W, both rated for T_J = –55°C to +150°C. Their TO-92 packaging, die size, and process technology (Process 63) result in equivalent junction-to-ambient thermal resistance. Therefore, PCB copper area, airflow, and mounting method determine actual thermal performance - not part-to-part variation between these two devices.

Can PN3645_D75Z be used in linear amplifier mode?

Yes, PN3645_D75Z supports linear operation with verified h_FE = 80–240 at I_C = 1–10 mA and V_CE = 10 V, and small-signal h_fe = 2.0 at 20 mA/20 V/100 MHz. Its low Cob (8.0 pF) and Cib (35 pF) minimize capacitive loading, enabling stable common-emitter gain up to ~100 kHz. Avoid sustained operation above 300 mW dissipation without heatsinking, as PD = 625 mW is derated above 25°C.