onsemi BC640G

Overview

BC640G from onsemi is a PNP silicon bipolar junction transistor rated for −80 V V_CEO, −500 mA continuous collector current, and 1.5 W power dissipation at T_C = 25°C, designed for medium-power linear and switching applications in industrial control, power supply regulation, and relay drivers.

For engineers reviewing the BC640G datasheet, pinout, applications, or equivalent options, key selection criteria include its −80 V V_CEO, h_FE range of 40–250 (depending on I_C), V_CE(sat) ≤ −0.5 V at I_C = −500 mA/I_B = −50 mA, TO-92 package thermal resistance (R_JC = 83.3°C/W), and Pb-free compliance per J-STD-609.

Technical Context

The BC640G operates as a general-purpose PNP BJT with fixed-emitter biasing capability and exhibits DC current gain (h_FE) from 40 at I_C = −150 mA to 250 at I_C = −500 mA, supporting both active-region amplification and saturated switching. Its f_T of 150 MHz enables use in low-frequency RF stages and fast-switching control circuits up to several megahertz.

Thermal design relies on case-to-heatsink conduction (R_JC = 83.3°C/W) rather than ambient convection (R_JA = 200°C/W), requiring mechanical mounting for sustained 1.5 W operation. The device features V_(BR)EBO = −5.0 V and C_ob = 9.0 pF, limiting base-emitter reverse voltage stress and high-frequency output capacitance.

Key Specifications

Pinout & Package

BC640G uses the TO-92 (Case 29, Style 14) plastic package with 3 leads: Emitter (Pin 1), Collector (Pin 2), Base (Pin 3), oriented with flat side facing viewer and leads downward.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC640-16G, BC640G offers broader h_FE tolerance for cost-sensitive designs where base drive margin exists; versus MJD127G, BC640G provides TO-92 footprint compatibility and lower assembly cost for sub-500 mA loads.

Availability

BC640G is available at Aetrix Electronics and suitable for industrial relay drivers, linear voltage regulator pass elements, and DC motor direction control circuits requiring stable component supply, Pb-free compliance, and TO-92 form factor compatibility.

Supply support for BC640G 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 specializing in energy-efficient power management, analog, sensors, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BC640G belongs to onsemi's legacy general-purpose bipolar transistor product line, engineered for reliability in industrial control, power conversion, and discrete switching applications where proven performance and long-term availability are essential.

FAQ

What is the maximum collector-emitter voltage rating for BC640G?

The BC640G has a guaranteed minimum V_(BR)CEO of −80 V at I_C = −10 mA with base open. This rating defines the absolute maximum reverse-biased voltage the transistor can withstand between collector and emitter before avalanche breakdown occurs. Operation above this voltage risks permanent damage. Designers should maintain at least 20% derating margin in safety-critical applications. The BC640G datasheet confirms this value under "OFF CHARACTERISTICS".

Does BC640G support saturated switching at 500 mA collector current?

Yes, BC640G supports saturated switching at I_C = −500 mA when driven with I_B ≥ −50 mA, achieving V_CE(sat) ≤ −0.5 V per the "ON CHARACTERISTICS" table. This ensures low conduction loss and efficient power transfer in relay drivers and power switches. The device's h_FE ≥ 40 at this operating point guarantees sufficient current gain to reach saturation with practical base drive levels.

Is BC640G RoHS-compliant and what does the 'G' suffix indicate?

Yes, BC640G is RoHS-compliant and the 'G' suffix explicitly denotes a Pb-free (lead-free) version per J-STD-609. It uses matte tin lead finish and meets JEDEC JS-001 ESD classification (HBM Class 3A). The 'G' variant replaces legacy BC640 in new designs requiring environmental compliance and modern soldering profiles, with identical electrical specs and TO-92 mechanical dimensions.

What is the thermal resistance from junction to case for BC640G?

The BC640G has a specified R_JC of 83.3°C/W, measured under standard test conditions with the case mounted to a large copper heatsink. This parameter is critical for calculating junction temperature rise when dissipating >625 mW. Unlike R_JA = 200°C/W (junction-to-ambient), R_JC reflects conduction-only path and requires mechanical mounting for accurate thermal modeling in BC640G applications.

How does BC640G differ from BC638G in terms of voltage ratings and gain?

The BC640G has higher voltage ratings than BC638G: V_CEO = −80 V vs. −60 V and V_CBO = −80 V vs. −60 V. Its h_FE minimum is also higher at I_C = −150 mA (40 vs. 25), making BC640G preferable in 48 V systems and designs requiring tighter base drive control. Both share identical TO-92 packaging, pinout, and thermal characteristics, enabling direct substitution where voltage margin permits.