1085-MMBT100A Equivalent & Substitute Parts

Part Overview

The 1085-MMBT100A is an NPN bipolar junction transistor manufactured by onsemi, designed for general-purpose switching and amplification applications. This device features a 45 V collector-emitter breakdown voltage, 500 mA maximum collector current, and 250 MHz transition frequency in a surface mount SOT-23 package. The part is classified as obsolete, making equivalent and substitute components necessary for ongoing production and maintenance applications. Substitute parts must maintain electrical compatibility across critical parameters including voltage ratings, current capacity, and frequency response while accommodating available packaging options.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Voltage - Collector Emitter Breakdown (Max)	45	V
Current - Collector (Ic) (Max)	500	mA
Power - Max	350	mW
Frequency - Transition	250	MHz
Operating Temperature Range	-55 to 150	°C
Package / Case	TO-236-3, SC-59, SOT-23-3	—
Mounting Type	Surface Mount	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the 1085-MMBT100A is determined by the following critical electrical and mechanical parameters:

Electrical Compatibility Criteria:

Transistor type must be NPN
Collector-emitter breakdown voltage must be equal to or greater than 45 V
Maximum collector current must be equal to or greater than 500 mA
Maximum power dissipation must be equal to or greater than 350 mW
Transition frequency must be equal to or greater than 250 MHz

Mechanical Compatibility Criteria:

Package must be surface mount in TO-236-3, SC-59, or SOT-23-3 form factor
Moisture sensitivity level must be 1 (Unlimited)
RoHS3 compliance required

Environmental Criteria:

Operating temperature range must encompass -55°C to 150°C or be compatible with application requirements
REACH unaffected status preferred for regulatory compliance

Substitute parts are grouped based on whether they meet all electrical requirements while maintaining package compatibility. Parts that exceed the specified parameters are acceptable substitutes provided they maintain the same physical footprint and pin configuration.

Parameter Comparison

Parameter	1085-MMBT100A	2SD1484KT146Q	2SD1484KT146R	BC817,215	BC817-25,215	BC817K-25R	BC817K25WH6433XTMA1	BCX19T116	MMBTA05-7-F
Transistor Type	NPN	NPN	NPN	NPN	NPN	NPN	NPN	NPN	NPN
Voltage - Collector Emitter Breakdown (Max) [V]	45	50	50	45	45	45	45	45	60
Current - Collector (Ic) (Max) [mA]	500	500	500	500	500	500	500	500	500
Power - Max [mW]	350	200	200	250	250	250	250	350	300
Frequency - Transition [MHz]	250	250	250	100	100	100	170	250	100
Operating Temperature (Max) [°C]	150	150	150	150	150	150	150	150	150
Package / Case	TO-236-3, SC-59, SOT-23-3	TO-236-3, SC-59, SOT-23-3	TO-236-3, SC-59, SOT-23-3	TO-236-3, SC-59, SOT-23-3	TO-236-3, SC-59, SOT-23-3	TO-236-3, SC-59, SOT-23-3	SC-70, SOT-323	TO-236-3, SC-59, SOT-23-3	TO-236-3, SC-59, SOT-23-3
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	Not Specified	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Product Status	Obsolete	Active	Active	Active	Active	Active	Last Time Buy	Not For New Designs	Active

Engineering Selection Recommendations

Primary Substitutes (Full Electrical and Mechanical Compatibility):

The following parts provide direct substitution with equivalent or superior electrical performance and identical package footprints:

BCX19T116 (Rohm Semiconductor) meets all electrical requirements with matching 45 V breakdown voltage, 500 mA collector current, 350 mW power rating, and 250 MHz transition frequency. This part is available in the same TO-236-3/SOT-23-3 package. However, the product status is listed as "Not For New Designs," limiting its use to legacy system maintenance.

2SD1484KT146R (Rohm Semiconductor) exceeds electrical specifications with 50 V breakdown voltage and 250 MHz transition frequency, maintaining 500 mA collector current. The power rating of 200 mW is lower than the original 350 mW specification. This part is active and widely available with 261,700 units in stock. The SMT3 package is mechanically compatible with SOT-23-3 footprints.

2SD1484KT146Q (Rohm Semiconductor) provides similar electrical performance to the 2SD1484KT146R variant with 50 V breakdown voltage and 250 MHz transition frequency. The power rating of 200 mW is lower than the original specification. This part is active with 8,402 units in stock.

Secondary Substitutes (Reduced Frequency Performance):

The BC817 family of parts from Nexperia and NXP provide electrical compatibility with reduced transition frequency specifications:

BC817-25,215 (NXP USA Inc.) offers 45 V breakdown voltage and 500 mA collector current with 250 mW power rating. The transition frequency is 100 MHz, which is below the original 250 MHz specification. This part is active with automotive qualification (AEC-Q101) and 1,000,400 units in stock.

BC817K-25R (Nexperia USA Inc.) provides identical electrical parameters to BC817-25,215 with 45 V breakdown voltage, 500 mA collector current, and 250 mW power rating. Transition frequency is 100 MHz. This part carries automotive qualification (AEC-Q100) and is available in tape and reel packaging with 3,764 units in stock.

BC817,215 (Nexperia USA Inc.) matches the electrical specifications of other BC817 variants with 45 V breakdown voltage, 500 mA collector current, and 250 mW power rating. Transition frequency is 100 MHz. This part is active with automotive qualification (AEC-Q101) and 32,200 units in stock.

Tertiary Substitute (Enhanced Voltage Rating):

MMBTA05-7-F (Diodes Incorporated) provides enhanced voltage performance with 60 V breakdown voltage, exceeding the original 45 V specification. Collector current remains at 500 mA with 300 mW power rating. Transition frequency is 100 MHz. This part is active with 47,100 units in stock and supports the full operating temperature range of -55°C to 150°C.

Package Consideration:

BC817K25WH6433XTMA1 (Infineon Technologies) is available in SC-70/SOT-323 package, which differs from the standard SOT-23-3 footprint of the original part. This package is smaller and requires PCB layout modification. The part provides 45 V breakdown voltage, 500 mA collector current, 250 mW power rating, and 170 MHz transition frequency. Product status is "Last Time Buy," limiting availability for new designs.

Recommendation Summary:

For applications requiring full electrical equivalence with 250 MHz transition frequency and 350 mW power dissipation, BCX19T116 is the closest match, though its "Not For New Designs" status restricts use to legacy applications. For active production, 2SD1484KT146R provides superior voltage performance and is widely available, though power dissipation is reduced to 200 mW. For applications where 100 MHz transition frequency is acceptable, the BC817 family offers multiple active options with automotive qualification and extensive inventory availability.

Frequently Asked Questions (FAQ)

Q: Can the 1085-MMBT100A be directly replaced with the 2SD1484KT146R?

A: The 2SD1484KT146R is electrically compatible for most applications. Both parts are NPN transistors with 500 mA collector current and 250 MHz transition frequency. The 2SD1484KT146R has a higher breakdown voltage (50 V vs. 45 V), which is acceptable. However, the power dissipation rating is lower (200 mW vs. 350 mW). Applications requiring the full 350 mW power rating must account for this reduction. The SMT3 package is mechanically compatible with SOT-23-3 footprints.

Q: What is the primary difference between the BC817 family and the original 1085-MMBT100A?

A: The BC817 family operates at 100 MHz transition frequency compared to the original 250 MHz specification. This reduced frequency performance is acceptable for low-speed switching applications but may not be suitable for high-frequency circuits. The BC817 variants maintain the same 45 V breakdown voltage and 500 mA collector current. All BC817 options carry automotive qualification, making them suitable for automotive applications.

Q: Why is the power dissipation rating different between substitute parts?

A: Power dissipation ratings reflect the maximum thermal capability of each device package and die design. The 2SD1484 series has a lower power rating (200 mW) due to package thermal characteristics, while the BCX19T116 matches the original 350 mW rating. Applications must ensure that actual power dissipation does not exceed the specified maximum for the selected substitute part.

Q: Are all substitute parts RoHS3 compliant?

A: All listed substitute parts are RoHS3 compliant except BC817-25,215, for which RoHS status is not specified in the provided data. For applications requiring RoHS3 compliance, verify the specific part number documentation or select from parts with confirmed ROHS3 Compliant status.

Q: Can the BC817K25WH6433XTMA1 be used as a direct replacement?

A: The BC817K25WH6433XTMA1 is not a direct replacement due to package differences. This part uses SC-70/SOT-323 package, which is physically smaller than the SOT-23-3 package of the original part. PCB layout modification is required for this substitution. Additionally, the product status is "Last Time Buy," indicating limited future availability.

Q: Which substitute part has the highest collector current rating?

A: All substitute parts listed maintain the 500 mA maximum collector current specification, matching the original 1085-MMBT100A. No substitute part exceeds this current rating.

Q: What is the operating temperature range for substitute parts?

A: Most substitute parts support a maximum operating temperature of 150°C. The MMBTA05-7-F specifically supports the full temperature range of -55°C to 150°C, matching the original part's operating range. Verify application temperature requirements when selecting substitutes.

Q: Is the 2SD1484KT146Q different from the 2SD1484KT146R?

A: Both 2SD1484 variants provide identical electrical specifications with 50 V breakdown voltage and 250 MHz transition frequency. The primary difference is the DC current gain specification: 2SD1484KT146Q has a minimum hFE of 120 at 10 mA/3V, while 2SD1484KT146R has a minimum hFE of 180 at the same conditions. The 2SD1484KT146R has significantly higher inventory availability (261,700 units vs. 8,402 units).

Q: Can the MMBTA05-7-F be used in high-voltage applications?

A: The MMBTA05-7-F has a 60 V breakdown voltage, which exceeds the original 45 V specification. This part is suitable for applications requiring higher voltage margins. However, the 100 MHz transition frequency is lower than the original 250 MHz, limiting use in high-frequency circuits.

Q: What packaging options are available for substitutes?

A: Most substitute parts are available in TO-236-3/SC-59/SOT-23-3 surface mount packages, maintaining compatibility with the original footprint. The BC817K25WH6433XTMA1 is available in the smaller SC-70/SOT-323 package, requiring PCB redesign. Packaging options include Cut Tape (CT), Digi-Reel, and Tape & Reel (TR) formats depending on the specific part number.

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