onsemi BC638G

Overview

BC638G from onsemi is a PNP silicon general-purpose bipolar junction transistor (BJT) rated for −60 V V_CEO, −500 mA continuous collector current, and 1.5 W power dissipation at T_C = 25°C, commonly used in low-voltage switching and linear amplification circuits in consumer and industrial power management.

For engineers reviewing the BC638G datasheet, pinout, applications, or equivalent options, key selection criteria include its −60 V breakdown rating, h_FE range of 25–160 at I_C = −5 mA to −500 mA, V_CE(sat) ≤ −0.5 V at I_C/I_B = 10, TO-92 package thermal resistance (R_JC = 83.3°C/W), and Pb-free compliance per J-STD-609.

Technical Context

The BC638G operates as a medium-power PNP BJT with fixed-emitter biasing capability and exhibits DC current gain (h_FE) that varies from 25 (min at I_C = −5 mA) to 160 (max at I_C = −150 mA), supporting both switching and analog amplification modes. Its f_T of 150 MHz enables use in audio-frequency signal paths and low-speed digital logic interfacing.

Thermal performance is defined by R_JC = 83.3°C/W and R_JA = 200°C/W, indicating suitability for PCB-mounted operation without heatsinking below ~300 mW dissipation. The device features V_BE(on) = −1.0 V and V_CE(sat) ≤ −0.5 V under specified drive conditions, confirming robust saturation behavior for switch-mode applications.

Key Specifications

Pinout & Package

BC638G is housed in a TO-92 (Case 29, Style 14) through-hole plastic package with 3 leads, optimized for manual assembly and low-cost PCB layouts. Pin 1 is Emitter, Pin 2 is Collector, Pin 3 is Base - verified per ON Semiconductor marking diagram and package outline drawing CASE 29-11.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC638G, BC639G serves complementary NPN roles in dual-transistor designs but demands layout changes, while BC640G offers direct functional substitution with enhanced voltage headroom-making it the preferred upgrade path for higher-rail applications without altering footprint or bias network.

Availability

BC638G is available at Aetrix Electronics and suitable for relay drivers, small DC motor controllers, linear regulator pass elements, and audio pre-amplifiers requiring stable component supply and Pb-free compliance.

Supply support for BC638G 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 manufacturer specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BC638G belongs to onsemi's legacy general-purpose bipolar transistor family, designed for cost-sensitive, medium-current switching and amplification in non-safety-critical industrial and consumer electronics.

FAQ

What is the maximum collector-emitter voltage rating for BC638G?

The BC638G has a maximum collector-emitter voltage (V_CEO) rating of −60 V DC. This value is tested under specified conditions (I_C = −10 mA, I_B = 0) and defines the absolute upper limit before avalanche breakdown occurs. Operating the BC638G above this voltage risks permanent damage, even briefly. Designers should maintain at least 20% derating margin in systems with voltage transients.

Does BC638G support Pb-free soldering processes?

Yes, BC638G is explicitly designated as a Pb-free device per ON Semiconductor's ordering nomenclature (the "G" suffix). It complies with J-STD-609 Class 3 moisture sensitivity and meets RoHS Directive 2011/65/EU requirements. The TO-92 package is qualified for standard lead-free reflow profiles with peak temperatures up to 260°C, and its marking includes the Pb-free microdot indicator per datasheet Figure 1.

What is the typical DC current gain (h_FE) of BC638G at different collector currents?

The BC638G exhibits h_FE = 25 (minimum) at I_C = −5 mA and V_CE = −2 V, rising to 40–160 at I_C = −150 mA under the same conditions. At I_C = −500 mA, h_FE remains ≥25 per datasheet Table "ON CHARACTERISTICS." This wide gain spread means base drive must be sized for worst-case h_FE to ensure saturation across temperature and unit variation.

Can BC638G be used in linear amplifier applications?

Yes, BC638G is suitable for linear amplification in audio-frequency ranges due to its f_T of 150 MHz and low input capacitance (C_ib = 110 pF). Its h_FE stability and V_BE(on) = −1.0 V support predictable biasing in common-emitter configurations. However, designers must limit power dissipation using the 1.5 W T_C rating and ensure adequate heatsinking for continuous operation above 300 mW.

How does BC638G differ from BC640G in practical design terms?

The BC638G and BC640G share identical package, pinout, thermal characteristics, and gain specifications-but differ in V_CEO (−60 V vs. −80 V) and V_CBO (−60 V vs. −80 V). In practice, BC640G allows safe operation in 48 V systems or with higher transient margins, while BC638G is optimized for 24 V and lower rails. No layout or bias changes are needed for substitution, though V_CEO derating must be re-verified.