KST56MTF Equivalent & Substitute Parts

Part Overview

The KST56MTF is a PNP bipolar junction transistor manufactured by onsemi, rated for 80 V collector-emitter breakdown voltage and 500 mA maximum collector current in a surface mount SOT-23-3 package. This device is classified as obsolete, indicating that direct replacement with active production alternatives is necessary for new designs and ongoing procurement.

The KST56MTF was designed for general-purpose switching and amplification applications requiring moderate voltage and current ratings. Due to its obsolete status, equivalent substitute parts from active manufacturers must be identified to maintain design continuity and ensure component availability for production and field service applications.

Key Parameters

Parameter	Value	Unit
Transistor Type	PNP	—
Current - Collector (Ic) Max	500	mA
Voltage - Collector Emitter Breakdown (Max)	80	V
Vce Saturation (Max) @ Ib, Ic	250 mV @ 10 mA, 100 mA	—
Current - Collector Cutoff (Max)	100	nA
DC Current Gain (hFE) Min @ Ic, Vce	50 @ 100 mA, 1 V	—
Power - Max	350	mW
Frequency - Transition	50	MHz
Mounting Type	Surface Mount	—
Package / Case	TO-236-3, SC-59, SOT-23-3	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—
Product Status	Obsolete	—

Substitute Part Grouping Explanation

Substitution of the KST56MTF is determined by strict equivalence across the following critical electrical and mechanical parameters:

Mandatory Equivalence Parameters:

Transistor Type: PNP
Collector-Emitter Breakdown Voltage: 80 V (maximum)
Maximum Collector Current: 500 mA
Package Type: SOT-23-3 (TO-236-3, SC-59)
Mounting Type: Surface Mount
Moisture Sensitivity Level: 1 (Unlimited)

Acceptable Variation Parameters:

Vce Saturation: Substitute parts may have equal or lower saturation voltage at specified test conditions
DC Current Gain (hFE): Substitute parts may have equal or higher minimum gain
Power Dissipation: Substitute parts may have equal or higher power rating
Frequency - Transition: Substitute parts may have equal or higher transition frequency
Operating Temperature Range: Substitute parts may have equal or wider temperature range

Substitute parts meeting all mandatory equivalence parameters are classified as direct replacements. Parts with enhanced electrical characteristics (higher gain, lower saturation voltage, higher frequency capability) remain functionally compatible within the KST56MTF application envelope.

Parameter Comparison

Part Number	Manufacturer	Ic (Max) mA	Vce Breakdown (Max) V	Vce Sat (Max) mV	hFE (Min)	Power (Max) mW	Frequency (Max) MHz	Package	Product Status	RoHS Status
KST56MTF	onsemi	500	80	250	50	350	50	SOT-23-3	Obsolete	—
MMBTA56LT1G	onsemi	500	80	250	100	225	50	SOT-23-3	Active	ROHS3 Compliant
MMBTA56LT3G	onsemi	500	80	250	100	225	50	SOT-23-3	Active	ROHS3 Compliant
2SB1198KT146Q	Rohm Semiconductor	500	80	500	120	200	180	SOT-23-3	Active	ROHS3 Compliant
2SB1198KT146R	Rohm Semiconductor	500	80	500	180	200	180	SOT-23-3	Active	ROHS3 Compliant
CMPT8599 TR PBFREE	Central Semiconductor Corp	500	80	300	100	350	150	SOT-23-3	Active	ROHS3 Compliant
CMPTA56 TR PBFREE	Central Semiconductor Corp	500	80	250	100	350	100	SOT-23-3	Active	ROHS3 Compliant
MMBTA56-7-F	Diodes Incorporated	500	80	250	100	300	50	SOT-23-3	Active	ROHS3 Compliant
MMBTA56-TP	Micro Commercial Co	500	80	250	100	225	50	SOT-23-3	Active	ROHS3 Compliant
MMBTA56Q-7-F	Diodes Incorporated	500	80	250	100	350	50	SOT-23-3	Active	ROHS3 Compliant

Engineering Selection Recommendations

All identified substitute parts are active production components with ROHS3 compliance, addressing the obsolescence of the KST56MTF. Selection among substitutes is based on the following criteria:

Primary Substitutes (Highest Compatibility):

MMBTA56LT1G, MMBTA56LT3G, MMBTA56-7-F, MMBTA56-TP, and MMBTA56Q-7-F maintain electrical characteristics most closely aligned with the KST56MTF. These parts preserve the 50 MHz transition frequency and 250 mV saturation voltage specification, with enhanced DC current gain (100 vs. 50 minimum). All are manufactured by onsemi, Diodes Incorporated, or Micro Commercial Co and carry ROHS3 compliance.

Secondary Substitutes (Enhanced Performance):

CMPTA56 TR PBFREE and CMPT8599 TR PBFREE offer higher transition frequency (100 MHz and 150 MHz respectively) and maintain 350 mW power rating matching the original KST56MTF. These parts are suitable for applications where increased frequency capability provides design margin.

Alternative Substitutes (Different Electrical Characteristics):

2SB1198KT146Q and 2SB1198KT146R from Rohm Semiconductor provide significantly higher transition frequency (180 MHz) and DC current gain but exhibit higher saturation voltage (500 mV vs. 250 mV) and lower power rating (200 mW vs. 350 mW). These parts are suitable only for applications where saturation voltage and power dissipation constraints are not limiting factors.

All substitute parts are available in active production status with unlimited moisture sensitivity level (MSL 1), ensuring long-term procurement viability.

Frequently Asked Questions (FAQ)

Q: Can MMBTA56LT1G directly replace KST56MTF in existing designs?

A: Yes. MMBTA56LT1G meets all mandatory equivalence parameters: PNP type, 80 V breakdown voltage, 500 mA collector current, SOT-23-3 package, and surface mount configuration. The higher DC current gain (100 vs. 50 minimum) and lower power rating (225 mW vs. 350 mW) do not prevent functional substitution in applications designed for the KST56MTF.

Q: What is the difference between MMBTA56LT1G and MMBTA56LT3G?

A: Both parts are manufactured by onsemi with identical electrical specifications. The difference is in packaging format: MMBTA56LT1G is supplied in Cut Tape (CT) & Digi-Reel format, while MMBTA56LT3G is supplied in Tape & Reel (TR) format. Electrical performance and package type (SOT-23-3) are identical.

Q: Why do 2SB1198KT146Q and 2SB1198KT146R have higher saturation voltage?

A: The 2SB1198 series from Rohm Semiconductor exhibits 500 mV saturation voltage at 50 mA base current and 500 mA collector current, compared to 250 mV for the KST56MTF at 10 mA base current and 100 mA collector current. This difference reflects different test conditions and device design. These parts are suitable for switching applications where saturation voltage is not a critical constraint.

Q: Are automotive-grade substitutes available?

A: Yes. MMBTA56-7-F and MMBTA56Q-7-F from Diodes Incorporated carry AEC-Q101 automotive qualification. Both maintain the 50 MHz transition frequency and 250 mV saturation voltage of the KST56MTF with enhanced DC current gain (100 minimum).

Q: What is the significance of PBFREE designation in part numbers?

A: PBFREE indicates lead-free construction, confirming ROHS3 compliance. CMPTA56 TR PBFREE and CMPT8599 TR PBFREE are explicitly marked as lead-free, while other substitutes (MMBTA56 series, 2SB1198 series) are inherently ROHS3 compliant without explicit designation in the part number.

Q: Can I use CMPT8599 TR PBFREE if my application requires 350 mW power dissipation?

A: Yes. CMPT8599 TR PBFREE is rated for 350 mW maximum power dissipation, matching the KST56MTF specification. This part also provides higher transition frequency (150 MHz) and maintains 250 mV saturation voltage at the specified test conditions.

Q: What packaging options are available for substitutes?

A: All substitute parts are supplied in SOT-23-3 (TO-236-3, SC-59) surface mount package, matching the KST56MTF. Packaging format varies: Cut Tape (CT) & Digi-Reel, Tape & Reel (TR), or both. Select packaging format based on procurement and assembly requirements.

Q: Is the KST56MTF still available for purchase?

A: The KST56MTF is classified as obsolete. While 6400 pieces are reported in stock, procurement of active production substitutes is recommended for new designs and long-term supply security.

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