onsemi BCW68G-ON

Overview

BCW68G from ON Semiconductor (formerly Fairchild) is a PNP bipolar junction transistor designed for general-purpose amplification and switching at up to 500 mA collector current. It features V_CEO = −45 V, I_C = −800 mA continuous, h_FE = 120–400 (at I_C = −10 to −300 mA), f_T = 100 MHz, and operates across −55°C to +150°C. It is commonly used in low-voltage linear amplifiers and discrete logic-level switching circuits.

For engineers reviewing the BCW68G datasheet, pinout, applications, or equivalent options, key selection criteria include its SOT-23 package compatibility, PNP polarity, −45 V V_CEO rating, thermal resistance of 357°C/W, and verified noise figure of 10 dB at 1 kHz - all critical for signal integrity and thermal design in compact analog and power-control stages.

Technical Context

The BCW68G is a silicon planar epitaxial PNP BJT fabricated using Fairchild's Process 63. Its structure supports stable DC current gain across wide collector current ranges (−10 mA to −300 mA) with minimal variation over temperature, and it delivers predictable saturation behavior (V_CE(sat) ≤ −1.5 V at I_C = −300 mA, I_B = −30 mA).

It exhibits low output capacitance (C_ob = 18 pF at V_CB = −10 V) and moderate input capacitance (C_ib = 105 pF at V_EB = −0.5 V), enabling reliable operation in audio-frequency amplifiers and medium-speed switching applications up to ~10 MHz. Its 100 MHz f_T confirms usable RF capability in narrowband VHF front-end stages.

Key Specifications

Pinout & Package

SOT-23 (JEDEC TO-236AB) 3-lead plastic surface-mount package with gull-wing leads; marking "DG" on top surface. Dimensions: 2.92 mm × 1.30 mm × 1.00 mm (L × W × H); recommended land pattern per MA03D Rev. 10.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BCW68G, BCW61G offers higher bandwidth but reduced voltage safety margin, while MMBT4403 trades minor V_CEO reduction for significantly improved f_T; BCW68G remains optimal where balanced gain, voltage rating, and noise performance are prioritized in general-purpose analog and power-control roles.

Availability

BCW68G is available at Aetrix Electronics and suitable for audio preamplifiers, discrete logic-level switches, and DC power path control requiring stable component supply, consistent parametric performance, and long-lifecycle availability.

Supply support for BCW68G 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

ON Semiconductor is a global semiconductor supplier specializing in energy-efficient power management, analog, sensors, and connectivity solutions for automotive, industrial, and consumer markets.

The BCW68G belongs to ON Semiconductor's legacy general-purpose bipolar transistor family, originally developed by Fairchild for cost-sensitive, high-reliability linear and switching applications in space-constrained designs.

FAQ

What is the maximum continuous collector current rating for the BCW68G?

The BCW68G has a maximum continuous collector current (I_C) rating of −800 mA at T_A = 25°C. Derating applies above ambient temperature: power dissipation must be reduced by 2.8 mW/°C, limiting practical sustained current in hot environments. This rating supports robust switching in relay drivers and power-path controls without forced cooling.

Does the BCW68G have a documented noise figure, and under what conditions is it specified?

Yes, the BCW68G has a measured noise figure (NF) of 10 dB, specified at I_C = −0.2 mA, V_CE = −5.0 V, R_S = 1.0 kΩ, f = 1.0 kHz, and BW = 200 Hz. This value reflects its suitability for low-noise preamplifier stages in sensor interfaces and portable audio, where minimizing added noise is critical to signal fidelity.

What is the pin configuration of the BCW68G in its SOT-23 package?

The BCW68G uses standard SOT-23 pinout: Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector. This matches JEDEC TO-236AB layout and is confirmed in the official MA03D package drawing. The device marking "DG" appears adjacent to Pin 1, enabling visual orientation during manual or automated placement.

Can the BCW68G be used in high-frequency amplifier applications?

Yes, the BCW68G has an f_T of 100 MHz, verified at I_C = −20 mA, V_CE = −10 V, and f = 100 MHz. This supports stable gain in VHF front-end amplifiers and broadband RF stages up to ~30 MHz, provided layout parasitics are minimized and bias networks maintain stability across frequency.

What is the thermal resistance (R_θJA) of the BCW68G, and how does it impact PCB layout?

The BCW68G has a junction-to-ambient thermal resistance (R_θJA) of 357°C/W when mounted on a standard FR-4 PCB (40 mm × 40 mm × 1.5 mm). This high value means even modest power dissipation (e.g., 100 mW) raises junction temperature by ~36°C above ambient - necessitating copper pour under the pad and careful trace width design to avoid thermal runaway.