onsemi BC239CTA

Overview

BC239CTA from Fairchild Semiconductor is an NPN epitaxial silicon transistor optimized for low-noise amplifier and switching applications, with h_FE 380–800 (Class C), V_CEO = 25 V, I_C = 100 mA, P_C = 500 mW, and f_T = 85 MHz at V_CE = 5 V, I_C = 10 mA - used in audio preamplifiers, signal conditioning stages, and general-purpose linear amplification.

For engineers reviewing the BC239CTA datasheet, pinout, applications, or equivalent options, key selection criteria include its Class C h_FE range, low noise figure (4 dB at 30–15 kHz), TO-92 package compatibility, V_CE(sat) ≤ 0.6 V at I_C = 100 mA, and suitability for low-voltage analog front-ends requiring stable DC gain and minimal thermal drift.

Technical Context

The BC239CTA operates as a discrete NPN bipolar junction transistor with epitaxial base construction, enabling high current gain consistency and low 1/f noise performance. Its design targets linear amplification where gain stability over temperature and collector current is critical, supported by specified h_FE min/max across I_C = 0.1–10 mA and V_CE = 5 V.

It features a fixed three-terminal configuration (Collector/Base/Emitter) with defined saturation voltages (V_CE(sat), V_BE(sat)) and capacitance parameters (C_ob = 3.5–6 pF, C_ib = 8 pF), making it suitable for medium-frequency small-signal amplification up to ~85 MHz under specified bias conditions.

Key Specifications

Pinout & Package

BC239CTA is housed in a standard TO-92 plastic package (3.60 × 4.58 × 4.58 mm max), lead-form compatible with through-hole assembly and manual prototyping. Pin identification follows JEDEC TO-92 outline: flat side facing viewer, leads down, left-to-right = Emitter–Base–Collector.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC239CTA, BC549C offers higher V_CEO but narrower noise-band specification, while 2N5089 provides wider h_FE range at the cost of unverified audio-band noise performance - BC239CTA remains optimal for precision low-noise, medium-frequency linear amplification.

Availability

BC239CTA is available at Aetrix Electronics and suitable for audio preamplifiers, sensor signal conditioners, general-purpose switching circuits, and DC power control modules requiring stable component supply and long-term manufacturability.

Supply support for BC239CTA 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 BC239CTA belongs to Fairchild's BC237/238/239 family of general-purpose NPN transistors designed specifically for low-noise audio amplification and reliable switching in consumer and industrial equipment.

FAQ

What is the h_FE range for BC239CTA?

The BC239CTA is binned as Class C with a guaranteed DC current gain (h_FE) range of 380 to 800 when measured at V_CE = 5 V and I_C = 2 mA. This tight gain distribution reduces design iteration time for bias networks and improves unit-to-unit consistency in production amplifiers and switches using BC239CTA.

Does BC239CTA support audio-frequency low-noise operation?

Yes, BC239CTA is explicitly characterized for low-noise performance: its noise figure is 4 dB at V_CE = 5 V, I_C = 0.2 mA, f = 30–15 kHz, and R_G = 2 kΩ - matching typical microphone preamp and audio line-driver requirements. This specification is unique to the BC239 variant within the BC237/238/239 family.

What is the maximum collector current rating for BC239CTA?

The BC239CTA has a maximum continuous collector current (I_C) rating of 100 mA at T_A = 25°C. Derating applies above 25°C ambient, with full rating maintained up to ~75°C on standard FR-4 PCB with minimal copper; actual usable current depends on thermal layout and V_CE drop in the BC239CTA application.

Is BC239CTA available in surface-mount packages?

No, BC239CTA is exclusively offered in the through-hole TO-92 package per Fairchild's original datasheet Rev. A2 (August 2002). No official SMD variant (e.g., SOT-23 or SC-59) was released for BC239CTA; design alternatives requiring surface mount must select functionally similar but distinct part numbers.

What is the collector-emitter saturation voltage of BC239CTA?

The BC239CTA exhibits V_CE(sat) ≤ 0.2 V at I_C = 10 mA / I_B = 0.5 mA and ≤ 0.6 V at I_C = 100 mA / I_B = 5 mA. These values confirm efficient switching behavior with minimal conduction loss, making BC239CTA suitable for low-power digital interfacing and LED driving where voltage headroom is constrained.