onsemi BC237_J35Z

Overview

BC237_J35Z from Fairchild Semiconductor is an NPN epitaxial silicon transistor optimized for low-noise amplifier and general-purpose switching applications, with V_CEO = 45 V, I_C = 100 mA, P_C = 500 mW, h_FE = 120–800 (Class A/B/C), and f_T = 150–250 MHz - used in audio preamplifiers, signal conditioning stages, and discrete logic interface circuits.

For engineers reviewing the BC237_J35Z datasheet, pinout, applications, or equivalent options, key selection considerations include its TO-92 package, low V_CE(sat) (0.07 V @ 10 mA/0.5 mA), high h_FE consistency across classifications, noise figure as low as 2 dB (BC237/238), and compatibility with 5 V–15 V biasing in linear and saturated operation.

Technical Context

The BC237_J35Z operates as a discrete bipolar junction transistor with epitaxial base construction enabling stable h_FE and low noise performance. Its DC current gain spans 120–800 depending on h_FE classification (A/B/C), and it supports both linear amplification (V_CE ≥ 1 V) and hard saturation (V_CE(sat) ≤ 0.2 V).

Designed for through-hole mounting, it features a fixed three-terminal configuration (Collector/Base/Emitter), specified under Ta = 25°C with derating above 25°C per thermal resistance R_θJA ≈ 200°C/W (TO-92). Junction temperature is rated to 150°C, and storage range extends from –55°C to +150°C.

Key Specifications

Pinout & Package

BC237_J35Z is housed in a standard TO-92 plastic package with 3.60 mm body width, 4.58 mm height, and 14.47 mm overall length. Leads are tinned copper, compatible with wave and hand soldering per J-STD-020.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN small-signal transistor applications.

Compared with BC547B and PN2222A, BC237_J35Z delivers uniquely balanced performance: lower noise than PN2222A, tighter h_FE binning than BC547B, and proven reliability in decades of audio and instrumentation designs - making it the preferred choice where gain stability and signal fidelity are prioritized over raw speed or power.

Availability

BC237_J35Z is available at Aetrix Electronics and suitable for audio preamplifier modules, discrete logic interface circuits, and RF buffer stages requiring stable component supply, long-term obsolescence resilience, and consistent parametric performance across production lots.

Supply support for BC237_J35Z 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 components before its acquisition by ON Semiconductor in 2016.

The BC237_J35Z belongs to Fairchild's legacy BC237/238/239 series - designed specifically for low-noise, general-purpose amplification and switching in cost-sensitive, high-reliability consumer and industrial equipment.

FAQ

What is the maximum collector-emitter voltage rating for BC237_J35Z?

The BC237_J35Z has a V_CEO rating of 45 V at T_A = 25°C, meaning it can safely withstand up to 45 V between collector and emitter with the base open. This rating decreases with rising ambient temperature and must be derated per the datasheet's thermal curves. Exceeding this voltage risks avalanche breakdown and permanent device failure. Always verify operating conditions against the absolute maximum ratings table in the BC237_J35Z datasheet.

Does BC237_J35Z have a specified noise figure, and under what conditions?

Yes, BC237_J35Z has a noise figure of 2 dB, measured at V_CE = 5 V, I_C = 0.2 mA, f = 1 kHz, and R_G = 2 kΩ - matching the BC237/238 specification. This low noise performance is confirmed for the BC237 variant group and applies directly to BC237_J35Z. It is not rated for BC239 (which specifies 4 dB at 30–15 kHz), so BC237_J35Z is preferred for sub-10 kHz analog signal paths where SNR is critical.

What h_FE classification does BC237_J35Z correspond to, and how is it marked?

BC237_J35Z corresponds to h_FE Class C, with a guaranteed DC current gain range of 380–800 at V_CE = 5 V and I_C = 2 mA. The "J35Z" suffix indicates Fairchild's internal marking code for Class C gain binning and TO-92 packaging. This classification enables predictable bias point setting in amplifier designs without post-manufacturing gain sorting.

Can BC237_J35Z be used in switching applications, and what is its typical V_CE(sat)?

Yes, BC237_J35Z is qualified for switching use with V_CE(sat) = 0.07 V at I_C = 10 mA and I_B = 0.5 mA, and 0.2 V at I_C = 100 mA and I_B = 5 mA. These low saturation voltages minimize conduction losses in relay drivers, LED controls, and digital interface circuits. Ensure base drive meets minimum I_B/I_C = 1/20 for reliable saturation, and verify thermal limits under pulsed or continuous duty.

Is BC237_J35Z RoHS compliant, and what is its lead finish?

BC237_J35Z was manufactured prior to RoHS enforcement (pre-2006) and carries a lead (Pb)-containing solder finish per Fairchild's Rev. A2 datasheet. It is not RoHS-compliant in its original form. For RoHS-compliant alternatives, consider modern equivalents like the MMBT2369 (SOT-23) or PN2222A (TO-92, RoHS-compliant variants), though parametric alignment with BC237_J35Z requires validation per application.