KST4403MTF Equivalent & Substitute Parts

Part Overview

The KST4403MTF is a PNP bipolar junction transistor manufactured by onsemi, rated for 40 V collector-emitter breakdown voltage and 600 mA maximum collector current in a surface mount SOT-23-3 package. This device is classified as obsolete product status. Direct equivalent and substitute parts are available from onsemi in active product status, offering improved availability and compliance certifications while maintaining electrical and mechanical compatibility.

Key Parameters

Parameter	Value
Transistor Type	PNP
Current - Collector (Ic) (Max)	600 mA
Voltage - Collector Emitter Breakdown (Max)	40 V
Vce Saturation (Max) @ Ib, Ic	750mV @ 50mA, 500mA
DC Current Gain (hFE) (Min) @ Ic, Vce	100 @ 150mA, 2V
Power - Max	350 mW
Frequency - Transition	200MHz
Package / Case	SOT-23-3 (TO-236)
Mounting Type	Surface Mount
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitute parts for the KST4403MTF are categorized into two groups based on electrical parameter compatibility:

Direct Equivalents maintain all critical electrical specifications: 600 mA maximum collector current, 40 V collector-emitter breakdown voltage, 200 MHz transition frequency, 100 minimum DC current gain at specified conditions, and identical saturation voltage characteristics. These parts are pin-compatible and functionally interchangeable in all applications where the KST4403MTF was used.

Similar Alternatives provide reduced maximum collector current (500 mA instead of 600 mA) and reduced transition frequency (100 MHz instead of 200 MHz), with higher collector-emitter breakdown voltage (45 V instead of 40 V). These parts are suitable for applications where the lower current and frequency specifications are acceptable, and the higher voltage rating provides additional design margin.

All substitute parts share the same SOT-23-3 package, surface mount mounting type, and MSL rating, ensuring mechanical and environmental compatibility.

Parameter Comparison

Part Number	Manufacturer	Product Status	Ic (Max)	Vce Breakdown (Max)	Vce Sat @ Ib, Ic	hFE (Min) @ Ic, Vce	Power (Max)	Frequency	Package	RoHS Status
KST4403MTF	onsemi	Obsolete	600 mA	40 V	750mV @ 50mA, 500mA	100 @ 150mA, 2V	350 mW	200MHz	SOT-23-3	REACH Unaffected
MMBT4403LT1G	onsemi	Active	600 mA	40 V	750mV @ 50mA, 500mA	100 @ 150mA, 2V	300 mW	200MHz	SOT-23-3	ROHS3 Compliant
MMBT4403LT3G	onsemi	Active	600 mA	40 V	750mV @ 50mA, 500mA	100 @ 150mA, 2V	300 mW	200MHz	SOT-23-3	ROHS3 Compliant
SMMBT4403LT1G	onsemi	Active	600 mA	40 V	750mV @ 50mA, 500mA	100 @ 150mA, 2V	300 mW	200MHz	SOT-23-3	ROHS3 Compliant
BC807-16LT1G	onsemi	Active	500 mA	45 V	700mV @ 50mA, 500mA	100 @ 100mA, 1V	300 mW	100MHz	SOT-23-3	ROHS3 Compliant
BC807-16LT3G	onsemi	Active	500 mA	45 V	700mV @ 50mA, 500mA	100 @ 100mA, 1V	300 mW	100MHz	SOT-23-3	ROHS3 Compliant
BC807-25LT1G	onsemi	Active	500 mA	45 V	700mV @ 50mA, 500mA	160 @ 100mA, 1V	300 mW	100MHz	SOT-23-3	ROHS3 Compliant
BC807-25LT3G	onsemi	Active	500 mA	45 V	700mV @ 50mA, 500mA	160 @ 100mA, 1V	300 mW	100MHz	SOT-23-3	ROHS3 Compliant
BC807-40LT1G	onsemi	Active	500 mA	45 V	700mV @ 50mA, 500mA	250 @ 100mA, 1V	300 mW	100MHz	SOT-23-3	ROHS3 Compliant
BC807-40LT3G	onsemi	Active	500 mA	45 V	700mV @ 50mA, 500mA	250 @ 100mA, 1V	300 mW	100MHz	SOT-23-3	ROHS3 Compliant
BC857ALT1G	onsemi	Active	100 mA	45 V	650mV @ 5mA, 100mA	125 @ 2mA, 5V	300 mW	100MHz	SOT-23-3	ROHS3 Compliant

Engineering Selection Recommendations

For Direct Replacement: Select MMBT4403LT1G, MMBT4403LT3G, or SMMBT4403LT1G. These parts maintain identical electrical specifications to the KST4403MTF while offering active product status and ROHS3 compliance. The choice between these three depends on packaging requirements: MMBT4403LT1G and SMMBT4403LT1G are supplied in Cut Tape format, while MMBT4403LT3G is supplied in Tape & Reel format. All three are manufactured by onsemi and carry REACH Unaffected status.

For Applications with Reduced Current Requirements: The BC807 series (BC807-16LT1G, BC807-16LT3G, BC807-25LT1G, BC807-25LT3G, BC807-40LT1G, BC807-40LT3G) provides active product status and ROHS3 compliance with 500 mA maximum collector current and 45 V breakdown voltage. These parts are suitable where the application does not require the full 600 mA current capability. The BC807-40 variants offer the highest DC current gain (250 minimum), while BC807-16 variants offer the lowest (100 minimum).

For Low-Current Applications: The BC857ALT1G is suitable only for applications requiring maximum 100 mA collector current and is not recommended as a general substitute for the KST4403MTF.

All recommended substitute parts are ROHS3 compliant and REACH unaffected, meeting modern regulatory requirements.

Frequently Asked Questions (FAQ)

Q: Can MMBT4403LT1G directly replace KST4403MTF in all applications?

A: Yes. MMBT4403LT1G maintains identical electrical specifications including 600 mA maximum collector current, 40 V breakdown voltage, 200 MHz transition frequency, and saturation voltage characteristics. The parts are pin-compatible in the SOT-23-3 package and functionally interchangeable.

Q: What is the difference between MMBT4403LT1G and MMBT4403LT3G?

A: Both parts have identical electrical specifications. The difference is packaging format: MMBT4403LT1G is supplied in Cut Tape (CT) & Digi-Reel format, while MMBT4403LT3G is supplied in Tape & Reel (TR) format. Selection depends on assembly equipment and procurement requirements.

Q: Can BC807-25LT1G replace KST4403MTF?

A: BC807-25LT1G is a similar alternative, not a direct equivalent. It provides 500 mA maximum collector current (versus 600 mA), 45 V breakdown voltage (versus 40 V), and 100 MHz transition frequency (versus 200 MHz). It is suitable only for applications where these reduced specifications are acceptable.

Q: Why is the KST4403MTF obsolete?

A: The KST4403MTF is classified as obsolete product status. Direct equivalents in active status (MMBT4403 series) are available from the same manufacturer with improved availability and compliance certifications.

Q: Are all substitute parts ROHS3 compliant?

A: All recommended substitute parts (MMBT4403LT1G, MMBT4403LT3G, SMMBT4403LT1G, and BC807 series) are ROHS3 compliant. The original KST4403MTF is REACH unaffected but does not carry ROHS3 certification.

Q: What is the difference between SMMBT4403LT1G and MMBT4403LT1G?

A: Both parts have identical electrical specifications and are supplied in Cut Tape format. The "S" prefix in SMMBT4403LT1G indicates a different manufacturing variant from onsemi. Electrical performance and pin compatibility are equivalent.

Q: Can I use BC857ALT1G as a substitute?

A: BC857ALT1G is not recommended as a general substitute. It is rated for only 100 mA maximum collector current, significantly lower than the KST4403MTF's 600 mA rating. Use only in applications specifically designed for 100 mA or lower collector current.

Q: What packaging options are available for direct equivalents?

A: Direct equivalents are available in two packaging formats: Cut Tape (CT) & Digi-Reel (MMBT4403LT1G, SMMBT4403LT1G) and Tape & Reel (TR) (MMBT4403LT3G). All use the SOT-23-3 package.

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