onsemi BC548TA

Overview

BC548TA from ON Semiconductor is a general-purpose NPN epitaxial silicon transistor in TO-92 package, rated for 30 V V_CEO, 100 mA I_C, and 500 mW P_C, with h_FE range of 420–800 (Class C), used in low-power switching and small-signal amplification circuits such as audio preamps and digital logic interfaces.

For engineers reviewing the BC548TA datasheet, pinout, applications, or equivalent options, this page delivers verified electrical parameters, TO-92 terminal mapping, noise performance (1.4–4.0 dB NF), saturation behavior (V_CE(sat) ≤ 600 mV at I_C = 100 mA), and direct alternatives for discrete BJT replacement in industrial and consumer designs.

Technical Context

This device operates as a medium-gain, low-noise NPN bipolar junction transistor optimized for linear amplification and saturated switching. Its V_EBO = 5 V, f_T = 300 MHz, and Cob = 3.5–6.0 pF support stable operation up to mid-VHF frequencies in bias-stable configurations.

Designed for DC-coupled and AC-coupled amplifier stages, it features low base-emitter on-voltage (V_BE(on) = 580–700 mV at I_C = 2 mA) and predictable h_FE classification-BC548TA corresponds to Class C per datasheet, ensuring consistent current gain across production lots.

Key Specifications

Pinout & Package

BC548TA uses the standard TO-92 3-lead plastic package with straight leads (JEDEC TO-92 compliant). Pin 1 is Collector, Pin 2 is Base, Pin 3 is Emitter - confirmed by Fairchild/ON Semiconductor mechanical drawings and ordering information.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC547CTA and 2N3904TA, BC548TA offers optimal balance of gain (420–800), noise (1.4–4.0 dB), and cost for 5–12 V signal conditioning and switching, while avoiding the pinout risk of 2N3904TA and the over-spec'd voltage rating of BC547CTA in low-voltage designs.

Availability

BC548TA is available at Aetrix Electronics and suitable for audio preamplifiers, relay driver circuits, and LED indicator control requiring stable component supply across prototyping, pilot production, and long-lifecycle industrial deployments.

Supply support for BC548TA 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

ON Semiconductor is a global semiconductor manufacturer specializing in energy-efficient power management, analog, and discrete components for automotive, industrial, and consumer markets.

BC548TA belongs to the legacy BC546–BC550 NPN/PNP transistor family originally developed by Fairchild and now maintained under ON Semiconductor's discrete portfolio for general-purpose analog and switching applications.

FAQ

What is the maximum collector-emitter voltage rating for BC548TA?

The BC548TA has a V_CEO rating of 30 V, meaning it can safely withstand up to 30 volts between collector and emitter with the base open. This value is specified in the Absolute Maximum Ratings table and must not be exceeded to prevent device breakdown. Designers should maintain at least 20% derating margin in production circuits, especially under temperature variation or transient conditions. The BC548TA datasheet confirms this rating applies specifically to the BC548 variant, not the broader BC546–BC550 family.

Is BC548TA pin-compatible with BC547 or BC546 variants?

Yes, BC548TA shares identical TO-92 package dimensions and pinout (Collector-Base-Emitter) with BC546, BC547, BC549, and BC550. All devices in this family follow JEDEC TO-92 mechanical standards with Pin 1 = Collector, Pin 2 = Base, Pin 3 = Emitter. However, electrical differences exist - notably V_CEO (30 V for BC548TA vs. 45 V for BC547 and 65 V for BC546) - so substitution requires verification of voltage and gain requirements in the target circuit. The BC548TA datasheet explicitly lists this shared pinout in the Physical Dimensions section.

What h_FE classification does BC548TA carry, and how is it marked?

BC548TA is classified as Class C, with h_FE ranging from 420 to 800 at V_CE = 5 V and I_C = 2 mA. Per the datasheet's h_FE Classification table, Class C devices are marked with "C" on the package body - for BC548TA, the marking is "BC548C". This classification is confirmed in the Ordering Information table, where BC548CTA denotes the Class C variant in ammo packaging. The BC548TA part number itself encodes both the base type (BC548) and gain grade (C).

Does BC548TA support low-noise audio applications?

Yes, BC548TA supports low-noise audio applications with a noise figure (NF) of 1.4–4.0 dB at V_CE = 5 V, I_C = 200 μA, and frequencies from 30 Hz to 15 kHz. This performance is documented in the Electrical Characteristics table and aligns with its designation as a low-noise variant within the BC546–BC550 family. It is commonly used in electret microphone preamplifiers and sensor signal conditioning where SNR preservation is critical. The BC548TA datasheet specifies this NF range separately from BC546/BC547, confirming its suitability for audio-grade amplification.

What is the power dissipation limit of BC548TA, and how does it scale with temperature?

BC548TA has a maximum collector power dissipation (P_C) of 500 mW at ambient temperature (T_A) = 25°C. Above 25°C, derating is required at 4.17 mW/°C - meaning P_C drops to 458 mW at 35°C and 333 mW at 65°C. This linear derating curve is defined in the Absolute Maximum Ratings table and reflects thermal resistance from junction-to-ambient (R_θJA ≈ 240°C/W). Designers must calculate actual power (V_CE × I_C) and verify junction temperature remains below 150°C using this derating rule. The BC548TA datasheet provides this exact derating slope in the Thermal Characteristics section.