2SC1740S-Q-AP Equivalent & Substitute Parts

Part Overview

The 2SC1740S-Q-AP is an NPN bipolar junction transistor manufactured by Micro Commercial Co, designed for general-purpose switching and amplification applications. This device features a maximum collector current of 150 mA, collector-emitter breakdown voltage of 50 V, and a transition frequency of 100 MHz. The part is classified as obsolete, necessitating identification of active equivalent components for continued system support and new designs. Substitute parts must maintain electrical compatibility across critical parameters including voltage ratings, current handling capacity, and thermal characteristics.

Key Parameters

Parameter	Value	Unit
Transistor Type	NPN	—
Current - Collector (Ic) Max	150	mA
Voltage - Collector Emitter Breakdown (Max)	50	V
Power - Max	300	mW
Frequency - Transition	100	MHz
Operating Temperature Range	-55 to 150	°C
Mounting Type	Through Hole	—
Package / Case	TO-92-3	—
DC Current Gain (hFE) Min	120	—

Substitute Part Grouping Explanation

Substitution of the 2SC1740S-Q-AP is determined by equivalence across the following critical electrical and mechanical parameters:

Electrical Compatibility Criteria:

Transistor type must be NPN
Maximum collector current (Ic) must be equal to or greater than 150 mA
Collector-emitter breakdown voltage (VCEO) must be equal to or greater than 50 V
Maximum power dissipation must support 300 mW operation
DC current gain (hFE) minimum must meet or exceed 120
Operating temperature range must encompass the required application range

Mechanical Compatibility Criteria:

Mounting type must be Through Hole
Package must be TO-92-3 or equivalent form factor
Lead configuration must be compatible with existing PCB layouts

The KSC945CYTA meets all substitution criteria while offering enhanced performance characteristics and active product status.

Parameter Comparison

Parameter	2SC1740S-Q-AP	KSC945CYTA	Unit
Manufacturer	Micro Commercial Co	onsemi	—
Product Status	Obsolete	Active	—
Transistor Type	NPN	NPN	—
Current - Collector (Ic) Max	150	150	mA
Voltage - Collector Emitter Breakdown (Max)	50	50	V
Vce Saturation (Max)	400 mV @ 100 mA, 2 A	300 mV @ 10 mA, 100 mA	V
Current - Collector Cutoff (Max)	100	100	nA
DC Current Gain (hFE) Min	120	120	—
Power - Max	300	250	mW
Frequency - Transition	100	300	MHz
Operating Temperature (Max)	150	150	°C
Mounting Type	Through Hole	Through Hole	—
Package / Case	TO-92-3	TO-92-3	—
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	—

Engineering Selection Recommendations

The KSC945CYTA is a direct electrical and mechanical substitute for the 2SC1740S-Q-AP. Both devices are classified as ROHS3 compliant and share identical voltage and current ratings. The primary distinction is product status: the 2SC1740S-Q-AP is obsolete, while the KSC945CYTA maintains active production status through onsemi.

Selection of the KSC945CYTA provides the following advantages:

Active Product Status: Ensures long-term availability and supply chain continuity
Enhanced Frequency Performance: Transition frequency of 300 MHz versus 100 MHz provides additional performance margin
Improved Saturation Characteristics: Lower Vce saturation voltage (300 mV) reduces power dissipation in switching applications
Regulatory Compliance: ROHS3 compliance maintained across both devices

The KSC945CYTA is suitable for direct replacement in existing 2SC1740S-Q-AP applications without circuit modification, provided thermal design accommodates the 250 mW maximum power rating.

Frequently Asked Questions (FAQ)

Q: Can the KSC945CYTA directly replace the 2SC1740S-Q-AP in existing designs?

A: Yes. Both devices share identical maximum collector current (150 mA), collector-emitter breakdown voltage (50 V), DC current gain minimum (120), and TO-92-3 package configuration. Direct substitution is electrically and mechanically compatible.

Q: What are the key differences between these two transistors?

A: The primary differences are product status (obsolete versus active), transition frequency (100 MHz versus 300 MHz), maximum power dissipation (300 mW versus 250 mW), and Vce saturation characteristics. The KSC945CYTA offers superior frequency performance and lower saturation voltage.

Q: Is the reduced maximum power rating of the KSC945CYTA (250 mW versus 300 mW) a concern?

A: The 250 mW rating of the KSC945CYTA is sufficient for applications designed for the 2SC1740S-Q-AP provided thermal design does not require operation at the absolute maximum power limit. Circuit analysis should confirm power dissipation remains within the 250 mW specification.

Q: Are both devices RoHS compliant?

A: Yes. Both the 2SC1740S-Q-AP and KSC945CYTA are ROHS3 compliant.

Q: What is the significance of the higher transition frequency in the KSC945CYTA?

A: The 300 MHz transition frequency of the KSC945CYTA provides improved high-frequency performance compared to the 100 MHz specification of the 2SC1740S-Q-AP. This characteristic does not negatively impact applications designed for lower frequencies and provides additional performance margin for frequency-dependent circuits.

Q: Are there any package or lead configuration differences?

A: Both devices utilize the TO-92-3 package with through-hole mounting. Physical form factors and lead configurations are compatible for direct PCB substitution.

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