2STA2121 Equivalent & Substitute Parts

Part Overview

The STMicroelectronics 2STA2121 is a PNP bipolar junction transistor rated for 250 V collector-emitter breakdown voltage and 17 A maximum collector current. This device is packaged in TO-264 through-hole configuration and rated for 220 W maximum power dissipation. The 2STA2121 is classified as obsolete product status. Identification of equivalent and substitute parts is necessary to support ongoing applications and procurement requirements where original inventory becomes unavailable.

Key Parameters

Parameter	Value	Unit
Transistor Type	PNP	—
Current - Collector (Ic) (Max)	17	A
Voltage - Collector Emitter Breakdown (Max)	250	V
Vce Saturation (Max) @ Ib, Ic	3V @ 800mA, 8A	—
Current - Collector Cutoff (Max)	5µA (ICBO)	—
DC Current Gain (hFE) (Min) @ Ic, Vce	80 @ 1A, 5V	—
Power - Max	220	W
Frequency - Transition	25	MHz
Operating Temperature (TJ)	150	°C
Mounting Type	Through Hole	—
Package / Case	TO-264-3, TO-264AA	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitute parts for the 2STA2121 are classified into two categories based on electrical parameter alignment:

Direct Substitutes meet or exceed all critical electrical parameters of the main part:

Collector current rating: 17 A (minimum requirement)
Collector-emitter breakdown voltage: 250 V (minimum requirement)
Saturation voltage: 3V @ 800mA, 8A (matching specification)
Collector cutoff current: 5µA (matching specification)
DC current gain: 80 @ 1A, 5V (matching specification)
Package compatibility: TO-264-3 or TO-264AA through-hole configuration

Similar Substitutes maintain core electrical ratings but exhibit variations in secondary parameters:

Collector current rating: 16 A (within 94% of 17 A specification)
Collector-emitter breakdown voltage: 250 V (matching specification)
Package compatibility: TO-264-3 or TO-264AA through-hole configuration
Variations in saturation voltage, cutoff current, DC current gain, power rating, and frequency response

Parameter Comparison

Parameter	2STA2121 (Main)	2SA1943OTU (Direct)	FJL4215OTU (Direct)	MJL21193G (Similar)
Manufacturer	STMicroelectronics	onsemi	Fairchild Semiconductor	onsemi
Product Status	Obsolete	Active	Active	Active
Transistor Type	PNP	PNP	PNP	PNP
Current - Collector (Ic) (Max)	17 A	17 A	17 A	16 A
Voltage - Collector Emitter Breakdown (Max)	250 V	250 V	250 V	250 V
Vce Saturation (Max) @ Ib, Ic	3V @ 800mA, 8A	3V @ 800mA, 8A	3V @ 800mA, 8A	4V @ 3.2A, 16A
Current - Collector Cutoff (Max)	5µA (ICBO)	5µA (ICBO)	5µA (ICBO)	100µA
DC Current Gain (hFE) (Min) @ Ic, Vce	80 @ 1A, 5V	80 @ 1A, 5V	80 @ 1A, 5V	25 @ 8A, 5V
Power - Max	220 W	150 W	150 W	200 W
Frequency - Transition	25 MHz	30 MHz	30 MHz	4 MHz
Operating Temperature (TJ)	150°C	-50°C ~ 150°C	-50°C ~ 150°C	-65°C ~ 150°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	TO-264-3, TO-264AA	TO-264-3, TO-264AA	TO-264-3, TO-264AA	TO-264-3, TO-264AA
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

Direct Substitutes (2SA1943OTU and FJL4215OTU):

The 2SA1943OTU and FJL4215OTU are classified as direct substitutes. Both parts maintain identical electrical specifications for collector current (17 A), collector-emitter breakdown voltage (250 V), saturation voltage (3V @ 800mA, 8A), collector cutoff current (5µA), and DC current gain (80 @ 1A, 5V). Both devices are active product status with ROHS3 compliance and REACH unaffected certification. The 2SA1943OTU is supplied by onsemi in TO-264-3 tube packaging. The FJL4215OTU is supplied by Fairchild Semiconductor in HPM F2 bulk packaging. Both support through-hole mounting in TO-264-3 and TO-264AA package configurations.

Similar Substitute (MJL21193G):

The MJL21193G is classified as a similar substitute. This onsemi device maintains the 250 V collector-emitter breakdown voltage and through-hole TO-264 package compatibility. The collector current rating is 16 A, representing a 94% retention of the 2STA2121 specification. The MJL21193G exhibits higher collector cutoff current (100µA versus 5µA), lower DC current gain (25 @ 8A, 5V versus 80 @ 1A, 5V), lower transition frequency (4 MHz versus 25 MHz), and lower maximum power rating (200 W versus 220 W). The MJL21193G is active product status with ROHS3 compliance and REACH unaffected certification.

Frequently Asked Questions (FAQ)

Q: Can the 2SA1943OTU directly replace the 2STA2121 in existing applications?

A: The 2SA1943OTU maintains identical electrical specifications for all critical parameters: 17 A collector current, 250 V breakdown voltage, 3V saturation voltage at specified bias conditions, 5µA collector cutoff current, and 80 hFE minimum gain. Both devices support through-hole TO-264 package mounting. The 2SA1943OTU is active product status, whereas the 2STA2121 is obsolete. Direct substitution is supported for applications where these electrical parameters are required.

Q: What are the differences between the 2SA1943OTU and FJL4215OTU?

A: Both parts are direct substitutes with identical electrical specifications. The primary differences are manufacturer (onsemi versus Fairchild Semiconductor) and packaging format (tube versus bulk). The 2SA1943OTU is supplied in tube packaging with TO-264-3 supplier device package designation. The FJL4215OTU is supplied in bulk packaging with HPM F2 supplier device package designation. Both support TO-264-3 and TO-264AA case configurations for through-hole mounting.

Q: When should the MJL21193G be considered as a substitute?

A: The MJL21193G is a similar substitute suitable for applications where the 16 A collector current rating is acceptable. This device maintains the 250 V breakdown voltage and through-hole package compatibility. Applications requiring the full 17 A collector current specification, higher DC current gain (80 minimum), or higher transition frequency (25 MHz) should use direct substitutes 2SA1943OTU or FJL4215OTU instead.

Q: Are all substitute parts RoHS3 compliant?

A: All substitute parts listed (2SA1943OTU, FJL4215OTU, and MJL21193G) are ROHS3 compliant and REACH unaffected. The original 2STA2121 is also ROHS3 compliant. All parts support equivalent environmental and regulatory compliance requirements.

Q: What is the impact of power rating differences between substitute parts?

A: The 2STA2121 is rated for 220 W maximum power dissipation. The 2SA1943OTU and FJL4215OTU are rated for 150 W, and the MJL21193G is rated for 200 W. Applications requiring sustained power dissipation above 150 W should evaluate thermal management requirements. The MJL21193G provides intermediate power rating at 200 W. Direct substitutes 2SA1943OTU and FJL4215OTU at 150 W are suitable for applications where power dissipation does not exceed this threshold.

Q: How do transition frequency differences affect circuit performance?

A: The 2STA2121 specifies 25 MHz transition frequency. Direct substitutes 2SA1943OTU and FJL4215OTU specify 30 MHz, providing higher frequency capability. The MJL21193G specifies 4 MHz, significantly lower than the original part. Applications requiring switching or amplification at frequencies approaching or exceeding 25 MHz should use direct substitutes. The MJL21193G is suitable only for lower-frequency applications below 4 MHz.

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