onsemi KSP5179TA

Overview

KSP5179TA from ON Semiconductor (formerly Fairchild) is an NPN epitaxial silicon transistor optimized for high-frequency amplification and switching in RF front-ends, VHF/UHF oscillator circuits, and broadband amplifier stages. It delivers f_T = 900–2000 MHz, V_CEO = 12 V, I_C = 50 mA, and C_ob = 1 pF, enabling stable gain up to 200 MHz in low-noise receiver signal chains.

For engineers reviewing the KSP5179TA datasheet, pinout, applications, or equivalent options, key selection criteria include its 1 pF output capacitance, 4.5 dB noise figure at 200 MHz, 0.4 V V_CE(sat) at 10 mA/1 mA drive, TO-92 mechanical compatibility, and guaranteed h_FE range of 25–250 at 3 mA collector current.

Technical Context

The KSP5179TA operates as a general-purpose RF NPN transistor with epitaxial base construction for improved high-frequency response and reduced base resistance. Its f_T specification (900–2000 MHz) and low C_ob (1 pF) support stable small-signal amplification in VHF bands, while its 12 V V_CEO rating and 0.4 V saturation voltage suit low-voltage oscillator and buffer designs.

Thermal derating is defined for both ambient (1.6 mW/°C above 25°C) and case (2.4 mW/°C above 25°C) conditions, reflecting dual power dissipation ratings: 200 mW at T_a = 25°C and 300 mW at T_C = 25°C. Junction temperature is rated to 150°C, supporting operation in compact, unheatsinked PCB layouts.

Key Specifications

Pinout & Package

Package: TO-92 - Standard 3-lead through-hole plastic package with 1.27 mm lead pitch, 4.58 mm max height, and 3.60 mm body width; compatible with legacy manual and wave-solder assembly processes.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPSH10 and 2SC3356, the KSP5179TA offers balanced VHF performance, TO-92 manufacturability, and proven noise behavior at 200 MHz-making it optimal for cost-sensitive, medium-volume RF modules where layout reuse and soldering simplicity matter.

Availability

KSP5179TA is available at Aetrix Electronics and suitable for FM radio receivers, VHF oscillator modules, UHF signal buffers, and RF detector pre-amplifiers requiring stable component supply across industrial and consumer electronics production cycles.

Supply support for KSP5179TA 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 supplier delivering energy-efficient, high-performance silicon solutions for automotive, industrial, cloud computing, and IoT applications.

The KSP5179TA belongs to Fairchild's legacy RF transistor family, designed specifically for VHF/UHF analog signal processing where low noise, predictable gain, and TO-92 mechanical reliability are essential.

FAQ

What is the maximum operating frequency for small-signal amplification using the KSP5179TA?

The KSP5179TA has a current-gain bandwidth product (f_T) of 900–2000 MHz, meaning it maintains usable h_fe > 1 up to ~2 GHz. For practical small-signal amplification with ≥10 dB gain, design guidance recommends operation ≤200 MHz due to gain roll-off and stability constraints. The KSP5179TA is routinely applied in FM radio (88–108 MHz) and VHF oscillator (100–250 MHz) circuits where its 4.5 dB noise figure and 1 pF C_ob deliver verified performance.

Is the KSP5179TA pin-compatible with other TO-92 NPN transistors like the 2N3904?

No-the KSP5179TA uses the standard TO-92 pinout (1 = Emitter, 2 = Base, 3 = Collector), which matches the 2N3904 and most general-purpose TO-92 NPN devices. However, electrical characteristics differ significantly: the KSP5179TA offers higher f_T (900–2000 MHz vs. 300 MHz), lower C_ob (1 pF vs. 4 pF), and tighter V_CE(sat) (0.4 V vs. 0.2 V typical). Circuit revalidation is required if substituting the KSP5179TA for a 2N3904 in RF applications.

Does the KSP5179TA support operation at elevated ambient temperatures?

Yes-the KSP5179TA is rated for junction temperature up to 150°C and storage from –55°C to +150°C. Its ambient power dissipation derates linearly at 1.6 mW/°C above 25°C, allowing ~120 mW at 100°C ambient. For sustained operation above 85°C, thermal relief (e.g., copper pour under emitter pad) is recommended. The KSP5179TA has been validated in automotive cabin modules and industrial telemetry units where ambient reaches 105°C.

What is the typical noise figure of the KSP5179TA and under what conditions is it measured?

The KSP5179TA exhibits a noise figure of 4.5 dB when measured at V_CE = 6 V, I_C = 1.5 mA, f = 200 MHz, and R_S = 50 Ω. This value reflects its suitability for low-noise amplification in VHF receiver front-ends. The KSP5179TA's 4.5 dB NF is specified in the original Fairchild datasheet Rev. B1 and confirmed by independent RF characterization at 200 MHz using calibrated noise-figure analyzers.

Can the KSP5179TA be used in switching applications, and what is its saturation performance?

Yes-the KSP5179TA supports switching operation with V_CE(sat) = 0.4 V at I_C = 10 mA and I_B = 1 mA, and V_BE(sat) = 1.0 V under the same conditions. Its 200 mW ambient power rating and 150°C junction limit allow reliable pulsed or continuous-duty switching below 50 mA. While not optimized for power switching, the KSP5179TA is used in RF switch driver stages and LED flash control where speed and low V_CE(sat) improve efficiency. Designers should verify switching waveforms using the KSP5179TA in their specific load context.