MCT2 Optoisolator Transistor with Base - Equivalent & Substitute Parts

Part Overview

The MCT2 is a 7500Vpk optoisolator with transistor output and base connection, manufactured by onsemi in a 6-DIP through-hole package. This component provides galvanic isolation for DC input signals with a single channel configuration. The MCT2 is classified as obsolete, making identification of active equivalent and substitute parts essential for ongoing design support and procurement.

Substiute Parts

MCT2M

onsemiIn Stock: 5251MCT2M Datasheet

Current PartRFQ

MCT2EM

onsemiIn Stock: 3886MCT2EM Datasheet

Parametric EquivalentRFQ

4N25-000E

Broadcom LimitedIn Stock: 30614N25-000E Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the MCT2 optoisolator is determined by the following critical parameters:

• Package compatibility: 6-DIP through-hole form factor
• Output configuration: Transistor with base connection
• Isolation voltage: Minimum 7500Vpk for parametric equivalents
• Current transfer ratio: Minimum 20% @ 10mA
• Output current capability: Minimum 50mA per channel
• Single channel configuration: 1 channel requirement
• Input type: DC input
• Operating temperature range: -40°C to 100°C minimum

Substitute parts are classified into two categories:

Parametric Equivalent: MCT2EM maintains identical electrical specifications and isolation voltage, differing only in product status (active vs. obsolete) and packaging format.

Similar Substitute: 4N25-000E provides compatible package and output configuration but operates at reduced isolation voltage (2500Vrms vs. 7500Vpk), increased output current capability, and extended temperature range.

Parameter Comparison

Engineering Selection Recommendations

MCT2EM is the primary substitute for obsolete MCT2 applications. Both parts are manufactured by onsemi with identical electrical specifications and isolation voltage ratings. MCT2EM is currently in active production status and carries ROHS3 compliance certification, making it suitable for new designs and legacy system maintenance where 7500Vpk isolation voltage is required.

4N25-000E serves as an alternative substitute when isolation voltage requirements can be reduced to 2500Vrms. This Broadcom Limited component maintains the same 6-DIP package and transistor-with-base output configuration. The 4N25-000E provides higher output current capability (100mA vs. 50mA) and extended lower temperature operating range (-55°C vs. -40°C). Selection of 4N25-000E requires confirmation that the reduced isolation voltage meets circuit requirements, as this represents a significant specification change from the original MCT2.

Both substitute parts carry ROHS3 compliance and REACH unaffected status, supporting modern procurement and environmental compliance requirements.

Frequently Asked Questions (FAQ)

Q: Can MCT2EM directly replace MCT2 in existing designs?

A: Yes. MCT2EM maintains identical electrical specifications, isolation voltage, output current, and operating temperature range as MCT2. The 6-DIP through-hole package is mechanically and electrically compatible. Pin configuration and functional behavior are equivalent.

Q: What is the key difference between MCT2EM and 4N25-000E?

A: The primary difference is isolation voltage. MCT2EM maintains 7500Vpk isolation matching the original MCT2, while 4N25-000E operates at 2500Vrms isolation. Additionally, 4N25-000E provides higher output current (100mA vs. 50mA) and slower switching times (3µs rise/fall vs. 2µs). Selection depends on circuit isolation voltage requirements.

Q: Are there any compliance or certification differences between these parts?

A: MCT2EM and 4N25-000E both carry ROHS3 compliance and REACH unaffected status. MCT2 (obsolete) does not list RoHS certification. For applications requiring modern environmental compliance, MCT2EM or 4N25-000E are preferred.

Q: Can 4N25-000E be used in high-voltage isolation applications originally designed for MCT2?

A: No. The 4N25-000E isolation voltage of 2500Vrms is significantly lower than MCT2's 7500Vpk rating. Use 4N25-000E only in applications where the reduced isolation voltage meets circuit safety and performance requirements. For applications requiring 7500Vpk isolation, MCT2EM is the appropriate substitute.

Q: What is the current transfer ratio specification, and is it consistent across all three parts?

A: Current transfer ratio (CTR) is specified as minimum 20% at 10mA input current for MCT2, MCT2EM, and 4N25-000E. This parameter is identical across all three parts and represents the ratio of output collector current to input LED current.

Q: Are there switching speed differences between MCT2EM and 4N25-000E?

A: Yes. MCT2EM specifies turn-on/turn-off times of 2µs and rise/fall times of 2µs/1.5µs. 4N25-000E specifies rise/fall times of 3µs/3µs with turn-on/turn-off times not specified. MCT2EM provides faster switching performance suitable for higher-frequency applications.