onsemi BC239BTA

Overview

BC239BTA from Fairchild Semiconductor is an NPN epitaxial silicon transistor optimized for low-noise amplifier and switching applications, with h_FE 180–460 (Class B), 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 small-signal switching.

For engineers reviewing the BC239BTA datasheet, pinout, applications, or equivalent options, key selection considerations include its Class B h_FE range, TO-92 package thermal limits, low-noise performance (NF = 4 dB at 30–15 kHz), V_BE(sat) ≤ 0.83 V, and verified suitability for linear amplification below 100 MHz.

Technical Context

The BC239BTA operates as a discrete NPN bipolar junction transistor with epitaxial base construction enabling stable gain and low noise. Its DC current gain classification (B: h_FE = 180–460) and f_T = 85 MHz support mid-frequency analog amplification, while V_CEO = 25 V and I_C = 100 mA define its safe operating area for low-power linear and switching use.

Designed for ambient-temperature operation (T_A = 25°C), it features V_CE(sat) ≤ 0.2 V at I_C = 10 mA / I_B = 0.5 mA and C_ob = 3.5–6 pF, making it suitable for high-fidelity audio gain stages and stable biasing in emitter-follower configurations without oscillation risk.

Key Specifications

Pinout & Package

BC239BTA is housed in a standard TO-92 plastic package with 3 leads: Collector (Lead 1), Base (Lead 2), Emitter (Lead 3), compliant with JEDEC TO-92 outline dimensions (3.60 ± 0.20 mm body width, 4.58 +0.25/–0.15 mm height).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC547B and 2N3904, BC239BTA offers tighter h_FE control (180–460), lower specified noise (4 dB), and optimized f_T/C_ob balance for audio-frequency amplification - making it preferable where gain consistency and signal fidelity are prioritized over raw bandwidth or voltage headroom.

Availability

BC239BTA is available at Aetrix Electronics and suitable for audio preamplifiers, sensor signal conditioning circuits, general-purpose switching loads, and emitter-follower buffers requiring stable component supply and long-term obsolescence management.

Supply support for BC239BTA 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 power management, analog, and discrete devices before its acquisition by ON Semiconductor in 2016.

The BC239BTA belongs to Fairchild's BC237/238/239 family of low-noise NPN transistors designed specifically for high-fidelity audio amplification and precision small-signal switching in consumer and industrial equipment.

FAQ

What is the h_FE range for BC239BTA?

The BC239BTA is binned as Class B, with a guaranteed DC current gain (h_FE) range of 180 to 460 when measured at V_CE = 5 V and I_C = 2 mA. This tight binning improves predictability in bias design for linear amplifier stages and reduces unit-to-unit variation in production assemblies using BC239BTA.

Is BC239BTA suitable for audio amplifier input stages?

Yes, BC239BTA is explicitly characterized for low-noise operation with a noise figure (NF) of 4 dB at V_CE = 5 V, I_C = 0.2 mA, and frequency 30–15 kHz - matching typical audio band requirements. Its low C_ob (3.5–6 pF) and stable h_FE make BC239BTA well-suited for microphone preamplifiers and line-level gain blocks.

What is the maximum collector current rating for BC239BTA?

The BC239BTA has a maximum continuous collector current (I_C) rating of 100 mA at T_A = 25°C. Derating is required above ambient temperature per its thermal resistance specification; operation beyond this limit risks thermal runaway or permanent device degradation. Always verify I_C in context of actual V_CE and duty cycle when using BC239BTA.

Does BC239BTA have a specified f_T value?

Yes, BC239BTA has a specified current-gain bandwidth product (f_T) of 85 MHz under test conditions V_CE = 5 V, I_C = 10 mA, and f = 100 MHz. This parameter confirms usable gain up to ~10 MHz in practical amplifier designs and supports stable operation in RF-adjacent signal paths where phase margin matters.

What package type does BC239BTA use?

BC239BTA uses the industry-standard TO-92 plastic package with lead configuration: Pin 1 = Collector, Pin 2 = Base, Pin 3 = Emitter. Its dimensions comply with JEDEC TO-92 outline specifications (body width 3.60 ± 0.20 mm, height 4.58 +0.25/–0.15 mm), ensuring compatibility with legacy through-hole assembly processes and socketing fixtures.