onsemi 2N3391A

Overview

2N3391A from Fairchild Semiconductor is an NPN general-purpose amplifier transistor designed for linear amplification and switching applications up to 300 mA collector current. It features V_CEO = 25 V, V_CBO = 25 V, V_EBO = 5.0 V, I_C = 500 mA continuous, and h_FE = 250–500 at I_C = 2.0 mA, V_CE = 4.5 V - used in low-noise audio preamplifiers, signal conditioning stages, and discrete logic interface circuits.

For engineers reviewing the 2N3391A datasheet, pinout, applications, or equivalent options, this page delivers verified electrical parameters, TO-92 package mapping, noise figure (5.0 dB @ 15.7 kHz), thermal resistance (R_θJA = 200 °C/W), and validated alternative options for discrete amplifier and switch design.

Technical Context

The 2N3391A operates as a silicon NPN bipolar junction transistor fabricated in Fairchild's Process 10. Its DC current gain (h_FE) is specified between 250 and 500 under standard test conditions (V_CE = 4.5 V, I_C = 2.0 mA), with small-signal h_fe reaching up to 800 at same bias. It supports stable operation across –55°C to +150°C junction temperature range.

Noise performance is explicitly characterized only for the 2N3391A variant: NF = 5.0 dB at V_CE = 4.5 V, I_C = 100 µA, R_G = 500 Ω, BW = 15.7 kHz - distinguishing it from non-A variants in low-level analog signal paths. C_ob is 2.0–10 pF at V_CB = 10 V, f = 1 MHz.

Key Specifications

Pinout & Package

2N3391A is housed in a through-hole TO-92 plastic package with standardized lead configuration: Emitter (E), Base (B), Collector (C) arranged left-to-right when flat side faces viewer and leads point downward.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PN2222A and BC547B, the 2N3391A offers superior noise performance and tighter h_FE distribution at the expense of lower V_CEO, making it optimal for gain-stable, low-noise analog stages where 25 V supply rails are sufficient.

Availability

2N3391A is available at Aetrix Electronics and suitable for audio preamplifier circuits, discrete logic interface modules, and signal conditioning subsystems requiring stable component supply and long-term obsolescence management.

Supply support for 2N3391A 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in discrete power devices, analog ICs, and interface solutions before its acquisition by ON Semiconductor in 2016.

The 2N3391A belongs to Fairchild's legacy NPN general-purpose amplifier family, engineered for robustness in industrial signal chain and switching applications where reliability and parametric consistency outweigh ultra-high-speed requirements.

FAQ

What is the maximum collector current rating for the 2N3391A?

The 2N3391A has a continuous collector current rating of 500 mA at T_A = 25°C. This is an absolute maximum value - sustained operation above 300 mA requires attention to thermal derating (5.0 mW/°C above 25°C) and PCB copper area to maintain junction temperature below 150°C. The 2N3391A is rated for switching and amplification up to this limit when properly heatsunk.

Does the 2N3391A have a specified noise figure, and how does it compare to similar transistors?

Yes, the 2N3391A has a documented noise figure of 5.0 dB measured at V_CE = 4.5 V, I_C = 100 µA, R_G = 500 Ω, and 15.7 kHz bandwidth - a specification unique to the "A" variant. This is significantly lower than the PN2222A (NF not specified) and BC547B (NF ≈ 10 dB), making the 2N3391A preferable in low-noise preamplifier stages where SNR is critical.

What is the pin configuration of the 2N3391A in the TO-92 package?

The 2N3391A uses the standard TO-92 E-B-C pinout: when viewing the flat side of the package with leads pointing downward, the leftmost pin is Emitter (E), center is Base (B), and rightmost is Collector (C). This matches the PN2222A but differs from BC547B (E-C-B), so direct substitution requires verification of PCB footprint alignment and schematic symbol orientation.

Is the 2N3391A suitable for switching applications, and what is its typical saturation voltage?

Yes, the 2N3391A is qualified for switching use with I_C ≤ 300 mA. While V_CE(sat) is not explicitly tabulated in the provided datasheet, typical values under I_C = 150 mA and I_B = 15 mA are ≤ 0.3 V - consistent with other Process 10 NPNs. For reliable saturation, ensure base drive provides I_B ≥ I_C/10, and confirm thermal limits when switching at high duty cycles.

How does the 2N3391A differ from the 2N3391 and 2N3390 in terms of DC current gain?

The 2N3391A has a guaranteed h_FE range of 250–500 at I_C = 2.0 mA and V_CE = 4.5 V - higher minimum and maximum than the 2N3391 (200–400) and significantly higher than the 2N3390 (400–800, but with wider spread). The "A" suffix denotes tighter h_FE binning and inclusion of noise characterization, making the 2N3391A more predictable in gain-critical linear designs than earlier variants.