onsemi 2N5551ZL1G

Overview

2N5551ZL1G from onsemi is an NPN silicon general-purpose amplifier transistor in TO-92 package, rated for V_CEO = 160 V, I_C = 600 mA, and f_T = 100–300 MHz, commonly used in low-noise preamplifier stages and switching applications up to 100 kHz.

For engineers reviewing the 2N5551ZL1G datasheet, pinout, applications, or equivalent options, key selection criteria include breakdown voltage margin, DC current gain (h_FE = 80–250 at I_C = 1–50 mA), saturation voltage (V_CE(sat) ≤ 0.25 V), thermal resistance (R_θJA = 200 °C/W), and Pb-free TO-92 packaging compliance.

Technical Context

This device operates as a medium-voltage, medium-current NPN bipolar junction transistor optimized for linear amplification and moderate-speed switching. Its design emphasizes high V_CBO (180 V) and low noise figure (NF = 8.0 dB at I_C = 250 µA), supporting stable gain in signal conditioning front-ends.

The 2N5551ZL1G shares the same die and electrical characteristics as the 2N5551G and 2N5551RLRPG variants, differing only in packaging format (tape-and-reel) and marking. It is not rated for automotive or safety-critical use and requires external biasing networks for stable operation.

Key Specifications

Pinout & Package

2N5551ZL1G is housed in a Pb-free TO-92 (Case 29-11) plastic package with straight leads, 5.20 mm maximum height, and standard 2.54 mm lead pitch. The package supports through-hole mounting and manual soldering per J-STD-020.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPSA42 and BC547C, the 2N5551ZL1G delivers balanced performance across voltage headroom (160 V), gain stability (h_FE 80–250), and noise (8.0 dB), making it the preferred choice for industrial analog front-ends where both robustness and fidelity matter.

Availability

2N5551ZL1G is available at Aetrix Electronics and suitable for industrial sensor interfaces, audio preamplifiers, and switch-mode power supply feedback circuits requiring stable component supply and long-term manufacturability.

Supply support for 2N5551ZL1G 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier delivering energy-efficient power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The 2N5551ZL1G belongs to onsemi's legacy discrete transistor product line, designed specifically for general-purpose amplification and switching in cost-sensitive, high-reliability industrial equipment.

FAQ

What is the maximum continuous collector current rating for the 2N5551ZL1G?

The 2N5551ZL1G has a maximum continuous collector current (I_C) rating of 600 mAdc at T_A = 25°C. Derating is required above this temperature - the device dissipates 625 mW at ambient, with a thermal resistance of 200 °C/W. At 70°C ambient, usable I_C drops to approximately 420 mA to stay within safe junction limits. This rating applies under free-air conditions; PCB copper area significantly improves thermal performance.

Does the 2N5551ZL1G have a specified noise figure, and under what conditions is it measured?

Yes, the 2N5551ZL1G has a specified noise figure of 8.0 dB, measured at I_C = 250 µA, V_CE = 5.0 Vdc, R_S = 1.0 kΩ, and f = 1.0 kHz. This value reflects its suitability for low-noise small-signal amplification, particularly in microphone preamplifiers and sensor signal conditioning. The noise figure increases at higher collector currents and frequencies, so design margins should be applied for precision analog applications.

Is the 2N5551ZL1G pin-compatible with the 2N2222A or PN2222A?

No, the 2N5551ZL1G is not pin-compatible with the 2N2222A or PN2222A despite sharing the TO-92 package. While all three use the same physical outline, their pinouts differ: 2N5551ZL1G uses E-B-C (Emitter-Base-Collector) order, whereas 2N2222A/PN2222A use E-C-B. Swapping them without board revision will cause circuit failure. Always verify pin mapping using the official onsemi datasheet for 2N5551ZL1G before substitution.

What is the guaranteed minimum DC current gain (h_FE) for the 2N5551ZL1G at 10 mA collector current?

The guaranteed minimum DC current gain (h_FE) for the 2N5551ZL1G is 80 at I_C = 10 mAdc and V_CE = 5.0 Vdc, per the onsemi datasheet. This is distinct from the 2N5550 variant, which guarantees only 60 under identical conditions. The 2N5551ZL1G's higher h_FE bin supports more stable biasing in production designs where gain variation must be minimized.

Can the 2N5551ZL1G be used in switching applications above 100 kHz?

The 2N5551ZL1G supports switching applications up to approximately 100 kHz in practical designs, based on its f_T = 100–300 MHz and documented turn-on/off times (t_r, t_f < 300 ns at I_C = 10 mA). However, switching efficiency degrades above 50 kHz due to minority-carrier storage time and lack of optimized charge control. For >200 kHz SMPS or digital logic interfacing, purpose-built RF transistors or MOSFETs are recommended instead of the 2N5551ZL1G.