onsemi BC237

Overview

BC237 from Fairchild Semiconductor is an NPN epitaxial silicon transistor designed for low-noise amplifier and general-purpose switching applications. It features a 45 V V_CEO, 100 mA I_C, 500 mW P_C, 150 MHz f_T, and h_FE range of 120–800 (Class A/B/C), commonly used in audio preamplifiers and signal conditioning stages.

For engineers reviewing the BC237 datasheet, pinout, applications, or equivalent options, key selection considerations include its TO-92 package, low V_CE(sat) (0.07 V @ 10 mA), noise figure (2 dB @ 1 kHz), h_FE classification options, and compatibility with BC238/BC239 in shared design footprints.

Technical Context

The BC237 operates as a discrete bipolar junction transistor with epitaxial base construction enabling high f_T and stable h_FE across temperature. Its low-noise performance (2 dB NF) and tight h_FE binning (A/B/C) support precision analog gain stages where gain consistency and signal integrity are critical.

Designed for DC-coupled and small-signal AC amplification, it supports V_CE up to 45 V and I_C up to 100 mA with thermal derating above 25°C. Saturation behavior is characterized at two operating points (10 mA/0.5 mA and 100 mA/5 mA), confirming suitability for both linear and switching roles.

Key Specifications

Pinout & Package

BC237 is housed in a standard TO-92 plastic package with 3 leads: Collector (lead 1), Base (lead 2), Emitter (lead 3). The package is through-hole mountable, with lead spacing of 1.27 mm (0.05"), overall length 4.58 mm, and maximum height 3.86 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC547 and 2N3904, BC237 offers superior noise performance (2 dB vs. ≥10 dB) and tighter h_FE binning-making it preferred for precision analog gain blocks where signal fidelity and repeatability outweigh raw speed or cost.

Availability

BC237 is available at Aetrix Electronics and suitable for audio preamplifier design, analog signal switching, and precision DC bias generation requiring stable component supply and long-term obsolescence management.

Supply support for BC237 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 discrete power and analog components before its acquisition by ON Semiconductor in 2016.

The BC237 belongs to Fairchild's legacy BC237/238/239 family of general-purpose NPN transistors engineered for low-noise amplification and reliable switching in consumer, industrial, and instrumentation electronics.

FAQ

What is the maximum collector-emitter voltage rating for BC237?

The BC237 has a V_CEO rating of 45 V at T_A = 25°C. This is the maximum voltage that can be applied between collector and emitter with the base open before breakdown occurs. Derating is required above 25°C ambient, and operation near this limit should include safety margin for transients. The BC237 datasheet specifies this value explicitly for the BC237 variant-not the BC238 or BC239.

Does BC237 have different hFE gain bins, and how are they marked?

Yes, BC237 is factory-binned into three h_FE classes: A (120–220), B (180–460), and C (380–800), measured at V_CE = 5 V and I_C = 2 mA. These variants are marked on the device body using suffix letters (e.g., BC237A, BC237B, BC237C), though the base part number BC237 refers to the full family. Each bin ensures predictable DC biasing in production designs.

What is the noise figure of BC237, and under what conditions is it specified?

The BC237 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. This specification applies specifically to the BC237 and BC238 variants; BC239 is rated at 4 dB under identical conditions. The low noise figure makes BC237 suitable for first-stage amplification in sensitive analog signal chains.

Is BC237 pin-compatible with BC238 or BC239?

Yes, BC237, BC238, and BC239 share identical TO-92 packaging and pinout: lead 1 = collector, lead 2 = base, lead 3 = emitter. They are mechanically and electrically interchangeable at the board level, though electrical parameters differ-especially V_CEO, V_CES, and noise figure. Designers may substitute within the same footprint but must verify circuit operating margins.

What is the typical current gain bandwidth product (fT) of BC237?

The BC237 has a typical f_T of 150 MHz, measured at V_CE = 3 V, I_C = 0.5 mA, and f = 100 MHz. This value reflects its small-signal high-frequency capability and supports use in RF amplifier stages up to ~50 MHz with adequate gain margin. The BC237 f_T is lower than BC239 (85 MHz) due to differing epitaxial layer optimization.