onsemi 2N5551CYTA

Overview

2N5551CYTA from ON Semiconductor is an NPN general-purpose amplifier transistor designed for high-voltage amplification and gas discharge display driver circuits. It features V_CEO = 160 V, I_C = 600 mA, h_FE = 180–240 (at I_C = 10 mA, V_CE = 5 V), P_D = 625 mW, and TO-92 package - commonly used in low-frequency switching and linear amplification stages of industrial power supplies and legacy display systems.

For engineers reviewing the 2N5551CYTA datasheet, pinout, applications, or equivalent options, key selection criteria include its high V_CEO rating, center-collector lead configuration (suffix "C"), and guaranteed h_FE band (suffix "Y") - critical for consistent biasing in analog gain stages and HV switch drivers where gain stability and breakdown margin are design-critical.

Technical Context

The 2N5551CYTA operates as a discrete silicon NPN bipolar junction transistor with fixed emitter-base and collector-base junction structures optimized for DC and low-frequency AC amplification. Its 180–240 h_FE range at 10 mA/5 V ensures predictable current gain in Class-A amplifier topologies, while V_CEO = 160 V and V_CBO = 180 V support operation in flyback snubbers and relay drivers with inductive kickback.

Thermal performance is defined by R_θJA = 200 °C/W (TO-92) and derating of 5.0 mW/°C above 25 °C, requiring heatsinking only above ~75 °C ambient in continuous 500 mA operation. Small-signal f_T = 100 MHz confirms suitability for audio and sub-MHz switching, not RF or high-speed digital applications.

Key Specifications

Pinout & Package

2N5551CYTA uses the TO-92 3-lead molded plastic package with center-collector pin configuration (suffix "C"): Pin 1 = Emitter, Pin 2 = Collector, Pin 3 = Base. The package is JEDEC-compliant, through-hole mountable, and rated for -55 °C to +150 °C operating junction temperature.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 2N5551TA and MPSA42, the 2N5551CYTA uniquely balances guaranteed mid-range h_FE, 160 V breakdown, and low V_BE(sat) - making it optimal for production-grade analog amplifiers and HV switch drivers where both gain stability and voltage margin are simultaneously required.

Availability

2N5551CYTA is available at Aetrix Electronics and suitable for gas discharge display drivers, linear audio preamplifiers, relay interface circuits, and legacy power supply feedback loops requiring stable component supply and long-term obsolescence management.

Supply support for 2N5551CYTA 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 (formerly Fairchild Semiconductor) is a global leader in energy-efficient semiconductor solutions for automotive, industrial, cloud computing, and consumer electronics.

The 2N5551CYTA belongs to ON Semiconductor's legacy general-purpose bipolar transistor product line, engineered for reliability in high-voltage analog and switching applications where robustness and parameter consistency outweigh ultra-high-speed requirements.

FAQ

What does the "CY" suffix mean in 2N5551CYTA?

The "C" in 2N5551CYTA denotes center-collector pinout (Pin 1 = Emitter, Pin 2 = Collector, Pin 3 = Base), and "Y" specifies guaranteed DC current gain (h_FE) of 180–240 at I_C = 10 mA and V_CE = 5 V. This dual-suffix coding ensures mechanical and electrical consistency for production designs relying on predictable gain and standardized layout. The 2N5551CYTA thus delivers repeatable performance in bias-critical amplifier and switch applications.

Can 2N5551CYTA replace 2N5551TA in existing designs?

Yes, the 2N5551CYTA is mechanically and electrically compatible with 2N5551TA - same TO-92 package, pinout, absolute maximum ratings, and thermal characteristics. The key upgrade is guaranteed h_FE = 180–240 versus 2N5551TA's minimum h_FE = 80. For designs already validated with 2N5551TA, substituting 2N5551CYTA improves gain consistency without layout or schematic changes. The 2N5551CYTA enhances reliability in production where h_FE spread previously required binning or trimming.

What is the maximum safe operating temperature for 2N5551CYTA?

The 2N5551CYTA has a maximum junction temperature (T_J) of +150 °C and storage temperature range of -55 °C to +150 °C. With R_θJA = 200 °C/W and P_D = 625 mW at 25 °C, continuous operation at full power requires ambient ≤ 75 °C. Derating begins at 5.0 mW/°C above 25 °C - so at 100 °C ambient, max dissipation drops to 250 mW. Thermal design must ensure the 2N5551CYTA stays within this envelope to avoid parametric shift or failure.

Is 2N5551CYTA suitable for switching applications above 1 MHz?

No - the 2N5551CYTA has f_T = 100 MHz but is not characterized or optimized for fast switching. Its typical t_on/t_off values are not specified, and V_CE(sat) = 0.15 V at 10 mA/1 mA suggests moderate speed. It performs reliably up to ~10 MHz in low-duty-cycle switching (e.g., display multiplexing), but for >100 kHz SMPS or digital logic interfacing, purpose-built RF or switching transistors (e.g., MMBT2222A) are preferred. The 2N5551CYTA excels in DC/low-frequency roles, not high-speed switching.

Does 2N5551CYTA require a heatsink in typical applications?

A heatsink is not required for 2N5551CYTA in most applications. At 25 °C ambient and 500 mA collector current, power dissipation is ~250 mW (assuming V_CE ≈ 0.5 V), well below its 625 mW rating. Even at 75 °C ambient, derated P_D remains ~375 mW. Standard TO-92 mounting on 1-in² FR-4 copper suffices for continuous operation up to ~400 mA. Heatsinking becomes relevant only in sealed enclosures >85 °C ambient or pulsed loads exceeding 600 mA - scenarios where the 2N5551CYTA's thermal limits must be explicitly verified.