2N6661-2 N-Channel MOSFET Equivalent & Substitute Parts

Part Overview

The 2N6661-2 is an N-Channel MOSFET manufactured by Vishay Siliconix, rated for 90V drain-to-source voltage with 860mA continuous drain current in a through-hole TO-39 package. This device is classified as obsolete, making identification of equivalent and substitute parts necessary for ongoing design support, maintenance, and production continuity. The part operates across a temperature range of -55°C to 150°C and dissipates up to 725mW at ambient temperature or 6.25W at case temperature.

Key Parameters

Parameter	Value	Unit
Drain-to-Source Voltage (Vdss)	90	V
Continuous Drain Current (Id) @ 25°C	860	mA
On-State Resistance (Rds On) @ 1A, 10V	4	Ohm
Gate-Source Threshold Voltage (Vgs(th)) @ 1mA	2	V
Maximum Gate-Source Voltage (Vgs)	±20	V
Input Capacitance (Ciss) @ 25V	50	pF
Power Dissipation (Max) @ Ambient	725	mW
Operating Temperature Range	-55 to 150	°C
Package Type	TO-39	—
Mounting Type	Through Hole	—

Substitute Part Grouping Explanation

Substitution of the 2N6661-2 is determined by strict equivalence across the following critical electrical and mechanical parameters:

Electrical Equivalence Criteria:

Drain-to-Source Voltage (Vdss): Must equal or exceed 90V
Continuous Drain Current (Id): Must equal or exceed 860mA
On-State Resistance (Rds On): Must not exceed 4 Ohm at specified conditions
Gate-Source Threshold Voltage (Vgs(th)): Must equal 2V at 1mA
Input Capacitance (Ciss): Must equal 50pF at 25V
Operating Temperature Range: Must span -55°C to 150°C

Mechanical Equivalence Criteria:

Package Type: TO-39 (TO-205AD, TO-39-3 Metal Can)
Mounting Type: Through Hole
FET Type: N-Channel
Technology: MOSFET (Metal Oxide Semiconductor)

The substitute part 2N6661 from Solid State Inc. meets all specified electrical and mechanical parameters for direct substitution.

Parameter Comparison

Parameter	2N6661-2 (Vishay Siliconix)	2N6661 (Solid State Inc.)	Match Status
FET Type	N-Channel	N-Channel	Equivalent
Technology	MOSFET (Metal Oxide)	MOSFET (Metal Oxide)	Equivalent
Drain-to-Source Voltage (Vdss)	90V	90V	Equivalent
Continuous Drain Current (Id) @ 25°C	860mA	900mA	Substitute Exceeds
On-State Resistance (Rds On) @ 1A, 10V	4 Ohm	4 mOhm	Substitute Superior
Gate-Source Threshold Voltage (Vgs(th)) @ 1mA	2V	2V	Equivalent
Maximum Gate-Source Voltage (Vgs)	±20V	±40V	Substitute Exceeds
Input Capacitance (Ciss) @ 25V	50pF	50pF	Equivalent
Power Dissipation (Max) @ Case Temperature	6.25W	6.25W	Equivalent
Operating Temperature Range	-55°C to 150°C	-55°C to 150°C	Equivalent
Package Type	TO-39	TO-39	Equivalent
Mounting Type	Through Hole	Through Hole	Equivalent

Engineering Selection Recommendations

Primary Substitute: 2N6661 (Solid State Inc.)

The 2N6661 from Solid State Inc. is the direct substitute for the obsolete 2N6661-2. This part maintains electrical and mechanical equivalence across all critical parameters while offering the following advantages:

Product Status: Active production status ensures ongoing availability and supply chain continuity
RoHS Compliance: ROHS3 compliant, meeting current environmental and regulatory requirements
Enhanced Specifications: Provides improved on-state resistance (4 mOhm versus 4 Ohm) and extended gate-source voltage rating (±40V versus ±20V), delivering superior performance margins in existing circuit designs
Inventory Availability: 4014 units in stock provide immediate procurement capability

The 2N6661 operates within identical voltage, current, and temperature parameters, ensuring direct functional replacement in all applications originally designed for the 2N6661-2.

Frequently Asked Questions (FAQ)

Q: Can the 2N6661 from Solid State Inc. be used as a direct replacement for the 2N6661-2?

A: Yes. The 2N6661 meets all electrical and mechanical specifications required for direct substitution. Both devices share identical drain-to-source voltage (90V), gate-source threshold voltage (2V), input capacitance (50pF), and operating temperature range (-55°C to 150°C). The TO-39 through-hole package is identical, enabling direct board-level replacement without circuit modification.

Q: What are the key differences between the 2N6661-2 and the 2N6661 substitute?

A: The substitute part provides three enhancements: (1) continuous drain current rating increased from 860mA to 900mA, (2) on-state resistance improved from 4 Ohm to 4 mOhm, and (3) maximum gate-source voltage extended from ±20V to ±40V. These improvements provide additional performance margin without affecting circuit compatibility.

Q: Are there any package or mounting differences between these parts?

A: No. Both the 2N6661-2 and 2N6661 use the TO-39 through-hole package (TO-205AD, TO-39-3 Metal Can). Mounting type, pin configuration, and physical dimensions are identical, allowing direct substitution on existing printed circuit boards.

Q: What is the significance of the RoHS compliance difference?

A: The 2N6661-2 is RoHS non-compliant, while the 2N6661 is ROHS3 compliant. For new designs or applications subject to environmental regulations, the ROHS3-compliant 2N6661 is required. For legacy system maintenance, either part may be acceptable depending on regulatory jurisdiction and customer requirements.

Q: Does the improved on-state resistance of the 2N6661 affect circuit design?

A: The 2N6661 exhibits lower on-state resistance (4 mOhm versus 4 Ohm), resulting in reduced power dissipation and improved efficiency. This enhancement is backward-compatible and does not require circuit redesign. Existing designs will benefit from improved thermal performance.

Q: Can the 2N6661 handle the same power dissipation as the 2N6661-2?

A: Yes. Both devices are rated for 6.25W power dissipation at case temperature. The improved on-state resistance of the 2N6661 may result in lower actual dissipation under identical operating conditions, providing additional thermal margin.

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