onsemi BC640

Overview

BC640 from onsemi is a PNP silicon bipolar junction transistor (BJT) rated for −80 V collector-emitter voltage, −500 mA continuous collector current, and 625 mW power dissipation at 25°C ambient. It features DC current gain (h_FE) of 25–250, saturation voltage (V_CE(sat)) ≤ −0.5 V at −500 mA/−50 mA drive, and 150 MHz transition frequency (f_T). It is used in medium-power linear amplification and switching applications such as relay drivers and power supply control stages.

For engineers reviewing the BC640 datasheet, pinout, applications, or equivalent options, key selection considerations include its TO-92 package compatibility, −80 V breakdown rating, guaranteed h_FE range across operating currents, thermal resistance (R_JA = 200°C/W), and Pb-free compliance per J-STD-609.

Technical Context

The BC640 operates as a general-purpose PNP BJT with fixed emitter-base and collector-base junction structures optimized for stable DC gain and low saturation voltage under moderate load conditions. Its f_T of 150 MHz supports audio-frequency amplification and fast-switching duty up to ~10 MHz with appropriate biasing.

Thermal design is constrained by R_JC = 83.3°C/W and R_JA = 200°C/W, requiring heatsinking or derating above 25°C ambient. The device exhibits V_BE(on) ≈ −1.0 V at −500 mA and maintains V_CE(sat) ≤ −0.25 V (typ.) when driven with I_B/I_C = 10.

Key Specifications

Pinout & Package

BC640 is housed in a TO-92 plastic package (Case 29, Style 14), with straight leads and bulk packaging. Pin 1 is Emitter, Pin 2 is Collector, Pin 3 is Base - confirmed per onsemi marking diagram and package outline drawing.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC640, BC639 offers complementary NPN functionality but demands schematic and layout changes, while MJD2955 delivers higher current capacity at the cost of board space and thermal complexity-neither is pin-compatible, and both require validation of gain, saturation, and thermal behavior in the target circuit.

Availability

BC640 is available at Aetrix Electronics and suitable for relay drivers, linear regulators, DC motor controls, and audio pre-amplifiers requiring stable component supply, consistent parametric performance, and Pb-free manufacturing compliance.

Supply support for BC640 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, sensing, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BC640 belongs to onsemi's legacy high-voltage PNP transistor family designed for robust, cost-effective discrete switching and amplification in industrial control, power conversion, and signal conditioning systems.

FAQ

What is the maximum continuous collector current rating for BC640?

The BC640 has a maximum continuous collector current (I_C) rating of −500 mA at T_A = 25°C. This value decreases with rising ambient temperature due to thermal derating (5.0 mW/°C above 25°C). At T_A = 70°C, usable I_C drops to approximately −300 mA. Always verify actual junction temperature using R_JA = 200°C/W and measured power dissipation in the final PCB layout.

Is BC640 pin-compatible with BC639 or BC640-16 variants?

No, BC640 is not pin-compatible with BC639 because BC639 is an NPN transistor with opposite polarity and different internal junction layout. BC640-016G is the exact same device as BC640-16; the "G" suffix denotes Pb-free packaging per onsemi's ordering nomenclature. Both share identical pinout (Emitter–Collector–Base), TO-92 package, and electrical specifications.

What is the typical V_CE(sat) for BC640 under standard switching conditions?

The BC640 exhibits a typical V_CE(sat) of −0.25 V when operated at I_C = −500 mA and I_B = −50 mA (I_C/I_B = 10). The maximum specified V_CE(sat) is −0.5 V under those same conditions. This low saturation voltage reduces power loss and improves efficiency in high-duty-cycle switching applications like relay or solenoid drivers.

Does BC640 meet RoHS and JEDEC standards for lead-free assembly?

Yes, BC640-016G is certified Pb-free and complies with RoHS Directive 2011/65/EU and JEDEC J-STD-609A Class 3 moisture sensitivity. It supports lead-free reflow profiles with peak temperatures up to 260°C and is qualified for standard SMT assembly processes without special handling beyond standard MSL-3 precautions.

Can BC640 be used in audio amplifier designs?

Yes, BC640 is suitable for low-to-medium power audio amplifier stages, including pre-amplifiers and driver stages. Its f_T of 150 MHz, low Cob (9.0 pF), and stable h_FE across I_C = −1 mA to −500 mA support bandwidths up to 150 kHz with low distortion. However, it is not optimized for ultra-low-noise or RF applications; verify THD and noise floor in the specific circuit configuration.