AO4850 MOSFET Equivalent & Substitute Parts

Part Overview

The AO4850 is a dual N-channel MOSFET array manufactured by Alpha & Omega Semiconductor Inc., rated for 75V drain-to-source voltage and 2.3A continuous drain current. This component is packaged in an 8-SOIC surface mount configuration and features logic level gate operation suitable for switching applications.

The AO4850 is classified as obsolete. Identifying equivalent and substitute parts is necessary to maintain design continuity, ensure supply chain availability, and support ongoing production requirements for applications utilizing this MOSFET array.

Key Parameters

Parameter	Value	Unit
Drain to Source Voltage (Vdss)	75	V
Continuous Drain Current (Id) @ 25°C	2.3	A
On-Resistance (Rds On) @ Id, Vgs	130 mOhm @ 3.1A, 10V	mOhm
Gate Threshold Voltage (Vgs(th)) @ Id	3	V @ 250µA
Gate Charge (Qg) @ Vgs	7	nC @ 10V
Input Capacitance (Ciss) @ Vds	380	pF @ 30V
Maximum Power Dissipation	1.1	W
Operating Temperature Range	-55 to 150	°C (TJ)
Configuration	2 N-Channel (Dual)
Package Type	8-SOIC
FET Feature	Logic Level Gate

Substitute Part Grouping Explanation

Substitution of the AO4850 MOSFET array is determined by the following critical parameters:

Mandatory Compatibility Criteria:

Configuration: 2 N-Channel (Dual) MOSFET array
Package Type: 8-SOIC surface mount
FET Feature: Logic Level Gate operation
Mounting Type: Surface Mount

Electrical Performance Criteria:

Drain-to-Source Voltage (Vdss): Must equal or exceed 75V
Continuous Drain Current (Id): Must equal or exceed 2.3A at 25°C
On-Resistance (Rds On): Lower values indicate improved performance
Gate Threshold Voltage (Vgs(th)): Must support logic level gate operation (typically 3-4V range)
Operating Temperature Range: Must encompass or exceed -55°C to 150°C

The substitute parts listed below meet or exceed the mandatory compatibility criteria and electrical performance requirements of the AO4850, enabling direct functional replacement in applications requiring dual N-channel MOSFET arrays with logic level gate control.

Parameter Comparison

Parameter	AO4850 (Main)	FDS3890	IRF7380TRPBF	NDS9945
Manufacturer	Alpha & Omega Semiconductor Inc.	onsemi	Infineon Technologies	onsemi
Product Status	Obsolete	Active	Active	Active
Configuration	2 N-Channel (Dual)	2 N-Channel (Dual)	2 N-Channel (Dual)	2 N-Channel (Dual)
Package / Case	8-SOIC	8-SOIC	8-SOIC	8-SOIC
FET Feature	Logic Level Gate	Logic Level Gate	Logic Level Gate	Logic Level Gate
Vdss (V)	75	80	80	60
Id @ 25°C (A)	2.3	4.7	3.6	3.5
Rds On (mOhm)	130 @ 3.1A, 10V	44 @ 4.7A, 10V	73 @ 2.2A, 10V	100 @ 3.5A, 10V
Vgs(th) (V)	3 @ 250µA	4 @ 250µA	4 @ 250µA	3 @ 250µA
Gate Charge Qg (nC)	7 @ 10V	35 @ 10V	23 @ 10V	30 @ 10V
Input Capacitance Ciss (pF)	380 @ 30V	1180 @ 40V	660 @ 25V	345 @ 25V
Power - Max (W)	1.1	0.9	2.0	0.9
Operating Temperature (°C)	-55 to 150	-55 to 175	-55 to 150	-55 to 150
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)
REACH Status	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected
ECCN	EAR99	EAR99	EAR99	EAR99

Engineering Selection Recommendations

FDS3890 (onsemi PowerTrench®)

The FDS3890 is an active product offering enhanced electrical performance relative to the AO4850. It provides higher drain current capability (4.7A versus 2.3A), improved on-resistance (44 mOhm versus 130 mOhm), and extended operating temperature range (-55°C to 175°C). The FDS3890 is RoHS3 compliant and maintains identical 8-SOIC packaging. This substitute is suitable for applications requiring higher current handling or improved thermal performance.

IRF7380TRPBF (Infineon HEXFET®)

The IRF7380TRPBF is an active product from Infineon Technologies featuring the HEXFET® series technology. It delivers 3.6A continuous drain current and 73 mOhm on-resistance, representing a balanced performance profile between the AO4850 and FDS3890. The IRF7380TRPBF supports the full operating temperature range of the AO4850 (-55°C to 150°C) and is RoHS3 compliant. This substitute provides moderate performance enhancement with proven reliability in established applications.

NDS9945 (onsemi)

The NDS9945 is an active product with specifications closely aligned to the AO4850 in terms of gate threshold voltage (3V) and operating temperature range (-55°C to 150°C). However, the NDS9945 is rated for 60V Vdss, which is below the AO4850 specification of 75V. The NDS9945 is suitable only for applications where the maximum voltage requirement does not exceed 60V. This substitute is RoHS3 compliant and offers comparable on-resistance performance (100 mOhm).

All substitute parts maintain identical package configuration (8-SOIC), logic level gate operation, dual N-channel configuration, and MSL rating (1 - Unlimited). All substitutes are REACH unaffected and classified as EAR99 for export control purposes.

Frequently Asked Questions (FAQ)

Q: Can the FDS3890 directly replace the AO4850 in all applications?

A: The FDS3890 meets all mandatory compatibility criteria: dual N-channel configuration, 8-SOIC package, logic level gate operation, and exceeds the AO4850 electrical specifications (80V Vdss, 4.7A Id). Direct substitution is supported from an electrical and mechanical standpoint. However, the higher gate charge (35 nC versus 7 nC) and input capacitance (1180 pF versus 380 pF) may affect switching speed and gate drive requirements in time-critical applications.

Q: Why does the NDS9945 have a lower Vdss rating than the AO4850?

A: The NDS9945 is rated for 60V Vdss, which is 15V below the AO4850 specification. This reflects different silicon technology and die design. The NDS9945 is suitable only for applications where the maximum drain-to-source voltage does not exceed 60V. Applications requiring 75V operation must use FDS3890 or IRF7380TRPBF.

Q: Are all substitute parts available in the same packaging?

A: Yes. All substitute parts (FDS3890, IRF7380TRPBF, and NDS9945) are packaged in 8-SOIC (0.154", 3.90mm width) surface mount configuration, identical to the AO4850. Pin-to-pin compatibility is maintained across all substitutes.

Q: What is the significance of the gate charge (Qg) difference between the AO4850 and substitutes?

A: Gate charge represents the total charge required to switch the MOSFET from off to on state. The AO4850 has a gate charge of 7 nC, while substitutes range from 23 nC to 35 nC. Higher gate charge requires greater gate drive current or longer switching times. Applications with fast switching requirements or limited gate drive capability should account for this parameter when selecting a substitute.

Q: Are all substitute parts RoHS compliant?

A: FDS3890, IRF7380TRPBF, and NDS9945 are all RoHS3 compliant. The AO4850 is classified as obsolete and does not carry an active RoHS certification status. Substitution with RoHS3 compliant parts ensures compliance with current environmental and regulatory requirements.

Q: Can the IRF7380TRPBF be used in applications requiring operation above 150°C?

A: No. The IRF7380TRPBF is rated for -55°C to 150°C operating temperature, matching the AO4850 specification. The FDS3890 extends to 175°C and is the only substitute supporting higher temperature operation.

Q: What is the impact of lower on-resistance (Rds On) in substitute parts?

A: Lower on-resistance reduces power dissipation during conduction, resulting in lower junction temperature and improved thermal performance. The FDS3890 (44 mOhm) and IRF7380TRPBF (73 mOhm) both provide significant improvement over the AO4850 (130 mOhm), enabling higher current handling or reduced heat generation in the same thermal environment.

Q: Are there any export control restrictions on these MOSFET substitutes?

A: All parts (AO4850, FDS3890, IRF7380TRPBF, and NDS9945) are classified as EAR99 and REACH unaffected, indicating no specific export control restrictions beyond standard semiconductor regulations. All parts maintain identical compliance status.

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