BC638-AP Equivalent & Substitute Parts

Part Overview

The BC638-AP is a PNP bipolar junction transistor manufactured by Micro Commercial Co, designed for small-signal switching and amplification applications. It features a maximum collector current of 1 A, collector-emitter breakdown voltage of 60 V, and a transition frequency of 100 MHz in a Through Hole TO-92 package. The BC638-AP is classified as obsolete, making identification of equivalent and substitute parts essential for ongoing design support and procurement continuity.

Substiute Parts

BC638-AP

Micro Commercial CoIn Stock: 999BC638-AP Datasheet

Current PartRFQ

BC638TA

Fairchild SemiconductorIn Stock: 9855BC638TA Datasheet

DirectRFQ

BC636TA

onsemiIn Stock: 7096BC636TA Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the BC638-AP is determined by strict equivalence across the following critical electrical and mechanical parameters:

Mandatory Matching Parameters:

• Transistor Type: PNP
• Current - Collector (Ic) (Max): 1 A
• Voltage - Collector Emitter Breakdown (Max): 60 V or greater
• Vce Saturation (Max) @ Ib, Ic: 500mV @ 50mA, 500mA
• Current - Collector Cutoff (Max): 100nA (ICBO)
• Frequency - Transition: 100MHz
• Mounting Type: Through Hole
• Package / Case: TO-92-3

Allowable Variations:

• DC Current Gain (hFE) (Min): Substitute parts may have lower minimum hFE values (40 vs. 100) while maintaining functional compatibility
• Power - Max: Substitute parts may have equal or greater power ratings (1 W vs. 830 mW)
• Operating Temperature: Substitute parts may have reduced lower temperature limit while maintaining upper limit compatibility

The BC638TA (Fairchild Semiconductor) qualifies as a direct substitute. The BC636TA (onsemi) qualifies as a similar substitute with reduced voltage rating (45 V vs. 60 V).

Parameter Comparison

Engineering Selection Recommendations

BC638TA (Direct Substitute - Recommended for Primary Selection)

The BC638TA from Fairchild Semiconductor is the preferred direct substitute for the BC638-AP. It maintains electrical equivalence across all critical parameters: 1 A collector current, 60 V breakdown voltage, 100 MHz transition frequency, and identical saturation characteristics. The BC638TA is classified as Active, ensuring long-term availability and supply chain stability. The increased power rating (1 W vs. 830 mW) provides additional thermal margin. The reduced DC current gain (40 vs. 100) does not compromise circuit functionality in applications where the BC638-AP was specified, as the lower gain value remains within acceptable operating ranges for typical small-signal switching circuits.

BC636TA (Similar Substitute - Conditional Selection)

The BC636TA from onsemi qualifies as a similar substitute with one critical limitation: the collector-emitter breakdown voltage is reduced to 45 V compared to the BC638-AP specification of 60 V. This part is suitable only for applications where the circuit design operates at or below 45 V. The BC636TA is classified as Last Time Buy, indicating limited future availability. All other electrical parameters match the BC638-AP, including collector current, saturation characteristics, transition frequency, and cutoff current. The BC636TA is ROHS3 compliant and maintains the same TO-92-3 package configuration.

Frequently Asked Questions (FAQ)

Q: Can the BC638TA be used as a direct replacement for the BC638-AP without circuit modification?

A: Yes. The BC638TA maintains electrical equivalence across all critical parameters required for the BC638-AP application. The reduced DC current gain (40 vs. 100) does not require circuit redesign in standard small-signal switching applications. The increased power rating provides additional design margin.

Q: What is the primary limitation of the BC636TA as a substitute?

A: The BC636TA has a maximum collector-emitter breakdown voltage of 45 V, compared to 60 V for the BC638-AP. This part is suitable only for circuits operating at or below 45 V. Applications requiring the full 60 V rating must use the BC638TA.

Q: Are all substitute parts available in the same TO-92-3 package?

A: Yes. Both the BC638TA and BC636TA are supplied in the TO-92-3 package with formed leads, identical to the BC638-AP. Direct board-level substitution is possible without PCB modification.

Q: What is the compliance status of the substitute parts?

A: The BC638TA compliance status is not specified in available documentation. The BC636TA is ROHS3 compliant. Both parts carry the EAR99 export classification.

Q: Why is the BC638-AP classified as obsolete?

A: The BC638-AP is no longer manufactured by Micro Commercial Co. The BC638TA and BC636TA represent current production alternatives from active manufacturers.

Q: Does the reduced operating temperature range of the BC638TA affect substitution suitability?

A: The BC638TA specifies an upper operating temperature of 150°C (TJ), matching the BC638-AP. The BC638-AP specifies a lower limit of -65°C, while the BC638TA does not specify a lower limit. For applications requiring operation below 0°C, the BC638TA specifications should be confirmed with the manufacturer.

Q: Are there differences in current-carrying capacity between the main part and substitutes?

A: No. All three parts (BC638-AP, BC638TA, and BC636TA) are rated for a maximum collector current of 1 A and identical saturation characteristics at 500mA.