onsemi BC237B

Overview

BC237B from Fairchild Semiconductor is an NPN epitaxial silicon transistor optimized for low-noise amplifier and general-purpose switching applications, with h_FE 180–460 at I_C = 2 mA, V_CE = 5 V, V_CEO = 45 V, P_C = 500 mW, and f_T = 150–250 MHz - used in audio preamplifiers, signal conditioning stages, and discrete logic interface circuits.

For engineers reviewing the BC237B datasheet, pinout, applications, or equivalent options, key selection criteria include DC current gain classification (Class B), collector-emitter saturation voltage (V_CE(sat) ≤ 0.2 V at I_C = 10 mA), noise figure (2 dB at 1 kHz), TO-92 mechanical compatibility, and thermal limits (T_J = 150°C).

Technical Context

The BC237B operates as a medium-speed, low-noise bipolar junction transistor with epitaxial base construction enabling stable h_FE across temperature and improved f_T performance versus planar alternatives. Its V_BE(on) of 0.55–0.7 V and low Cob (3.5–6 pF) support high-fidelity small-signal amplification up to mid-VHF range.

Designed for linear and switching roles in discrete analog subsystems, it features guaranteed h_FE binning (Class B: 180–460), tight V_CE(sat) control (0.07–0.2 V), and specified noise figure (2 dB @ 1 kHz, RG = 2 kΩ), distinguishing it from BC237A (lower h_FE) and BC237C (higher h_FE, higher NF).

Key Specifications

Pinout & Package

BC237B is housed in a standard through-hole TO-92 package (3.60 × 4.58 × 1.02 mm), with lead spacing compliant to JEDEC TO-92 outline. Pin 1 is Collector, Pin 2 is Base, Pin 3 is Emitter - verified per Fairchild Rev. A2 datasheet Figure "Package Dimensions" and pin diagram.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC547B and 2N3904, BC237B offers superior noise performance (2 dB vs. 5 dB) and tighter h_FE consistency (180–460 vs. 100–300), making it preferred for precision analog front-ends where gain stability and SNR are critical.

Availability

BC237B is available at Aetrix Electronics and suitable for audio preamplifier design, discrete logic interface implementation, and RF buffer circuit development requiring stable component supply and long-term obsolescence management.

Supply support for BC237B 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 manufacturer specializing in discrete power devices, analog ICs, and optoelectronics before its acquisition by ON Semiconductor in 2016.

The BC237B belongs to Fairchild's legacy BC237/238/239 family - designed specifically for low-noise, medium-frequency amplifier and switching applications in consumer audio, instrumentation, and industrial control systems.

FAQ

What is the h_FE range for BC237B at I_C = 2 mA and V_CE = 5 V?

The BC237B is binned to Class B with a guaranteed DC current gain (h_FE) range of 180 to 460 under test conditions of V_CE = 5 V and I_C = 2 mA. This specification is confirmed in the Fairchild BC237/238/239 Rev. A2 datasheet, Table "hFE Classification", and distinguishes BC237B from BC237A (120–220) and BC237C (380–800). The BC237B provides tighter gain consistency than generic 2N3904 variants.

Is BC237B suitable for low-noise audio amplifier applications?

Yes, BC237B is explicitly characterized for low-noise operation with a noise figure of 2 dB at 1 kHz, V_CE = 5 V, I_C = 0.2 mA, and R_G = 2 kΩ - per Fairchild Rev. A2 datasheet Section "Electrical Characteristics". Its low V_BE(on) variation and tight h_FE binning further support stable biasing in microphone preamps and sensor interfaces where SNR is critical. BC237B outperforms BC547B (4 dB) and 2N3904 (5 dB) in this metric.

What is the maximum collector current rating for BC237B?

The absolute maximum DC collector current (I_C) for BC237B is 100 mA, as specified in the "Absolute Maximum Ratings" table of the Fairchild BC237/238/239 Rev. A2 datasheet. Continuous operation at this level requires adherence to thermal derating curves - power dissipation must remain ≤500 mW, and junction temperature must not exceed 150°C. At I_C = 100 mA, V_CE(sat) is guaranteed ≤0.6 V.

Does BC237B have a defined pinout, and what is the package type?

Yes, BC237B uses the standard TO-92 package with a confirmed pinout: Pin 1 = Collector, Pin 2 = Base, Pin 3 = Emitter - documented in the "Package Dimensions" section and pin diagram of the Fairchild Rev. A2 datasheet. This pinout is identical across BC237/238/239 variants and compatible with industry-standard TO-92 footprints. No alternate pinouts or package variants exist for BC237B.

How does BC237B compare to BC239 in terms of noise performance?

BC239 is the low-noise variant of the family, rated at 4 dB noise figure over 30–15 kHz (vs. BC237B's 2 dB at 1 kHz), while BC237B delivers superior low-frequency noise performance. The BC237B datasheet specifies 2 dB NF at 1 kHz, making it more suitable for audio preamplifiers and DC-coupled sensor interfaces. BC239 trades LF noise for extended HF linearity - neither is a drop-in replacement for the other without circuit re-optimization.