onsemi BC547TA

Overview

BC547TA from ON Semiconductor is a general-purpose NPN epitaxial silicon transistor in TO-92 package, rated for 45 V V_CEO, 100 mA I_C, and 500 mW P_C, with h_FE range of 200–450 (Class B), widely used in low-power switching and linear amplification circuits such as signal buffering in sensor interfaces and discrete logic level translation.

For engineers reviewing the BC547TA datasheet, pinout, applications, or equivalent options, this page delivers verified electrical parameters, TO-92 terminal mapping, real-world use cases in industrial control and consumer electronics, and two confirmed alternative transistors with documented h_FE and voltage rating differences.

Technical Context

This device operates as a bipolar junction transistor with fixed emitter-base and collector-base junctions optimized for DC amplification and saturated switching. Its h_FE classification (B) ensures predictable current gain between 200 and 450 at V_CE = 5 V and I_C = 2 mA, while V_CE(sat) ≤ 250 mV at I_C = 10 mA / I_B = 0.5 mA confirms low-loss on-state performance.

Designed for ambient temperatures up to 150°C junction operation, it supports continuous DC biasing and pulse applications with f_T = 300 MHz - sufficient for audio-frequency amplification and sub-MHz digital signal conditioning without parasitic oscillation concerns.

Key Specifications

Pinout & Package

BC547TA uses the standard TO-92 3-lead plastic package with straight leads (JEDEC TO-92 compliant). Dimensions match Fairchild/ON Semiconductor mechanical drawings Rev. 1.1.1, with lead spacing of 0.2 inch and body height ≤ 4.6 mm.

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, BC547TA offers identical transistor performance to BC547B with enhanced supply chain traceability, while providing higher V_CEO and broader h_FE range than 2N3904 - making it preferable for new designs targeting industrial voltage margins and gain stability.

Availability

BC547TA is available at Aetrix Electronics and suitable for industrial sensor interface, discrete logic translation, and LED driver applications requiring stable component supply, long-term obsolescence management, and RoHS-compliant through-hole sourcing.

Supply support for BC547TA 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 power management, analog, sensing, and connectivity solutions for automotive, industrial, and consumer markets.

BC547TA belongs to ON Semiconductor's legacy general-purpose transistor product line, originally developed by Fairchild Semiconductor to deliver cost-effective, reliable NPN switching and amplification for mass-market electronics.

FAQ

What is the maximum collector-emitter voltage rating for BC547TA?

The BC547TA has a maximum collector-emitter voltage (V_CEO) rating of 45 V. This value is specified in the Absolute Maximum Ratings table of the official ON Semiconductor datasheet (Rev. 1.1.1) and applies at T_A = 25°C. Exceeding this voltage risks avalanche breakdown and permanent device failure. Designers should maintain at least 20% derating margin - i.e., limit operating V_CE to ≤36 V in production systems - especially under temperature variation or transient conditions.

Does BC547TA have a defined h_FE classification, and what does it mean for circuit design?

Yes, BC547TA is classified as Class B, with a guaranteed DC current gain (h_FE) range of 200 to 450 when measured at V_CE = 5 V and I_C = 2 mA. This classification directly impacts bias network design: for example, a 10 mA collector load requires base current between 22 μA and 50 μA. Using the full h_FE spread ensures amplifier stability across manufacturing variance and temperature drift without recalculating resistor values per unit.

Is BC547TA pin-compatible with other transistors like 2N2222 or PN2222?

No, BC547TA is not pin-compatible with 2N2222 or PN2222. Although all three use TO-92 packages, their pinouts differ: BC547TA follows the standard Fairchild/ON Semiconductor arrangement (1 = Collector, 2 = Base, 3 = Emitter), whereas 2N2222 variants commonly use 1 = Emitter, 2 = Base, 3 = Collector. Swapping them without board revision will cause circuit failure. Always verify pinout diagrams from the respective datasheets before substitution.

What is the typical noise figure of BC547TA, and in which applications does it matter?

The BC547TA exhibits a noise figure of 2.0–10.0 dB at 1 kHz with V_CE = 5 V, I_C = 200 μA, and R_G = 2 kΩ - consistent with its BC546/BC547 family designation. This makes it suitable for low-noise preamplifier stages in audio front-ends, sensor signal conditioning, and instrumentation amplifiers where maintaining signal-to-noise ratio above 60 dB is essential. It is not recommended for ultra-low-noise RF front-ends where BC549/BC550 variants would be preferred.

Can BC547TA be used in switching power supply feedback circuits?

BC547TA is not recommended for primary switching or high-frequency PWM feedback paths in modern switching power supplies. While its f_T = 300 MHz suggests RF capability, its relatively slow storage time (not specified in the datasheet) and lack of guaranteed switching speed parameters make it unsuitable for >100 kHz duty-cycle control. It can be used safely in auxiliary functions - such as optocoupler driver stages or enable/disable logic - where switching frequency remains below 10 kHz and timing precision is non-critical.