onsemi 2N3859A_D75Z

Overview

2N3859A_D75Z from Fairchild Semiconductor is an NPN epitaxial silicon transistor designed for general-purpose amplification and switching in low-to-medium power circuits, with V_CEO = 60 V, I_C = 500 mA continuous, h_FE = 75–200 at I_C = 1.0 mA, f_T = 90–250 MHz, and TO-92 package. It serves in audio preamplifiers, relay drivers, and signal conditioning stages where moderate gain and bandwidth are required.

For engineers reviewing the 2N3859A_D75Z datasheet, pinout, applications, or equivalent options, key selection criteria include DC current gain range, collector-emitter breakdown voltage, thermal resistance (R_θJA = 200 °C/W), junction temperature limits (–55 to +150 °C), and TO-92 mechanical compatibility.

Technical Context

This NPN bipolar junction transistor operates in active mode for linear amplification and saturation/cutoff for digital switching. Its h_FE variation (75–200) reflects process-controlled gain binning, and f_T ≥ 90 MHz supports RF-capable small-signal amplification up to VHF band edges.

Thermal design relies on R_θJA = 200 °C/W and P_D = 625 mW at T_A = 25 °C, derating 5.0 mW/°C above ambient. Breakdown voltages (V_CEO, V_CBO, V_EBO) are symmetrically rated at 60 V, 60 V, and 6.0 V respectively, defining safe operating area boundaries.

Key Specifications

Pinout & Package

2N3859A_D75Z is housed in a standard TO-92 plastic package with 3 leads. Lead spacing and body dimensions conform to JEDEC TO-92 outline (14.47 mm length, 4.58 mm width, 3.60 mm height).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 2N3859A_D75Z, the 2N2222A trades voltage ruggedness for higher f_T, while the BC547B sacrifices current drive for tighter h_FE distribution and lower noise-making each suitable only where those specific trade-offs align with system requirements.

Availability

2N3859A_D75Z is available at Aetrix Electronics and suitable for audio preamplifiers, relay driver circuits, and signal level shifter designs requiring stable component supply across industrial control, test equipment, and legacy system repair programs.

Supply support for 2N3859A_D75Z 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 analog and discrete semiconductor manufacturer, acquired by ON Semiconductor in 2016; known for high-reliability bipolar transistors and power devices.

The 2N3859A_D75Z belongs to Fairchild's legacy NPN general-purpose amplifier family, engineered for cost-sensitive, medium-speed analog and switching functions in industrial and consumer electronics.

FAQ

What is the maximum continuous collector current for the 2N3859A_D75Z?

The 2N3859A_D75Z supports a maximum continuous collector current of 500 mA at T_A = 25 °C. Derating applies above ambient temperature-consult the thermal resistance (R_θJA = 200 °C/W) and power dissipation (P_D = 625 mW) specs to determine safe operating current at elevated temperatures. The 2N3859A_D75Z must not exceed this limit without external heatsinking or airflow.

Does the 2N3859A_D75Z have a specified V_CE(sat) value?

The official Fairchild datasheet for the 2N3859A_D75Z does not list a guaranteed V_CE(sat) parameter. However, typical saturation behavior can be inferred from h_FE and I_C ratings: at I_C = 500 mA and sufficient base drive (I_B ≥ I_C/10), V_CE(sat) generally falls below 0.5 V. For precise switching design, empirical validation or substitution with a device specifying V_CE(sat) is recommended. The 2N3859A_D75Z remains appropriate for non-critical saturation applications.

Is the 2N3859A_D75Z RoHS compliant?

The 2N3859A_D75Z was manufactured prior to RoHS enforcement deadlines and predates standardized lead-free packaging requirements. It contains lead in solder and die attach materials, and is not RoHS compliant per EU Directive 2011/65/EU. For new designs requiring compliance, consider modern alternatives such as the MMBT2222ALT1G or PN2222A. The 2N3859A_D75Z remains viable for legacy repair and non-regulated industrial applications.

What is the pin configuration of the 2N3859A_D75Z in TO-92 package?

The 2N3859A_D75Z uses standard TO-92 pinout: Pin 1 is Emitter, Pin 2 is Collector, Pin 3 is Base-viewed with flat side facing outward and leads pointing down. This configuration is consistent across Fairchild's 2N3859A series and matches JEDEC TO-92 mechanical drawings. No alternate pinouts or variants exist for the 2N3859A_D75Z; correct orientation is essential to avoid reverse-bias damage during circuit operation.

Can the 2N3859A_D75Z replace the 2N3904 in existing designs?

The 2N3859A_D75Z is not a direct replacement for the 2N3904 due to significant differences: I_C (500 mA vs. 200 mA), P_D (625 mW vs. 625 mW), and h_FE range (75–200 vs. 100–300). While both are TO-92 NPN transistors, the 2N3859A_D75Z delivers higher current but lower minimum gain. Substitution may cause bias instability or excessive power dissipation in 2N3904-optimized circuits. Verify thermal and gain margins before using the 2N3859A_D75Z as a 2N3904 alternative.