RN1905FE,LF(CT Pre-Biased Bipolar Transistor Equivalent & Substitute Parts

Part Overview

The RN1905FE,LF(CT is a pre-biased dual NPN bipolar transistor manufactured by Toshiba Semiconductor and Storage in SOT-563/SOT-666 surface mount packaging. This component is classified as a 2 NPN pre-biased transistor rated for 50V collector-emitter breakdown voltage, 100mA maximum collector current, and 100mW power dissipation. The device is actively produced and ROHS3 compliant with unlimited moisture sensitivity rating.

Equivalent and substitute parts are necessary when the primary part experiences supply constraints, extended lead times, or when design flexibility permits selection from multiple qualified sources. Substitute parts must maintain electrical compatibility across critical parameters including collector current rating, voltage breakdown specifications, base and emitter-base resistor values, and frequency response characteristics.

Key Parameters

Parameter	Value	Unit
Transistor Type	2 NPN - Pre-Biased (Dual)	—
Current - Collector (Ic) (Max)	100	mA
Voltage - Collector Emitter Breakdown (Max)	50	V
Resistor - Base (R1)	2.2	kOhms
Resistor - Emitter Base (R2)	47	kOhms
DC Current Gain (hFE) (Min) @ Ic, Vce	80 @ 10mA, 5V	—
Vce Saturation (Max) @ Ib, Ic	300 @ 250µA, 5mA	mV
Current - Collector Cutoff (Max)	500	nA
Frequency - Transition	250	MHz
Power - Max	100	mW
Mounting Type	Surface Mount	—
Package / Case	SOT-563, SOT-666	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution eligibility for the RN1905FE,LF(CT is determined by strict alignment with the following critical parameters:

Primary Substitution Criteria:

Transistor configuration: 2 NPN pre-biased dual or 1 NPN + 1 PNP pre-biased dual
Maximum collector current: 100mA minimum
Collector-emitter breakdown voltage: 50V minimum
Base resistor (R1): 2.2kOhms (exact match required for direct substitution)
Emitter-base resistor (R2): 47kOhms (exact match required for direct substitution)
DC current gain (hFE): 80 minimum @ 10mA, 5V
Vce saturation: 300mV maximum @ 250µA, 5mA
Transition frequency: 250MHz minimum
Surface mount packaging: SOT-563 or SOT-666 compatible
Compliance: ROHS3 compliant, MSL 1 rating

Substitution Categories:

Direct Substitutes (Identical Resistor Configuration): Parts with matching R1 (2.2kOhms) and R2 (47kOhms) values that maintain all other electrical specifications.

Functional Equivalents (Alternative Resistor Configuration): Parts with different base or emitter-base resistor values that meet or exceed all other electrical parameters. These parts function in similar applications but may require circuit evaluation for specific bias point requirements.

Limited Compatibility (Different Transistor Type): Parts with 1 NPN + 1 PNP configuration instead of 2 NPN. These are functionally equivalent for many applications but differ in internal transistor topology.

Parameter Comparison

Part Number	Manufacturer	Transistor Type	Ic (Max) mA	Vce(br) (Max) V	R1 (Base) kOhms	R2 (Emitter-Base) kOhms	hFE (Min) @ Ic, Vce	Vce Sat (Max) @ Ib, Ic mV	Frequency MHz	Power (Max) mW	Package	Product Status
RN1905FE,LF(CT	Toshiba	2 NPN	100	50	2.2	47	80 @ 10mA, 5V	300 @ 250µA, 5mA	250	100	SOT-563, SOT-666	Active
EMH10T2R	Rohm	2 NPN	100	50	22	22	56 @ 5mA, 5V	300 @ 500µA, 10mA	250	150	SOT-563, SOT-666	Active
DCX114EH-7	Diodes Inc.	1 NPN, 1 PNP	100	50	10	10	30 @ 5mA, 5V	300 @ 500µA, 10mA	250	150	SOT-563, SOT-666	Active
DCX114YH-7	Diodes Inc.	1 NPN, 1 PNP	100	50	10	47	68 @ 10mA, 5V	300 @ 250µA, 5mA	250	150	SOT-563, SOT-666	Active
DCX123JH-7	Diodes Inc.	1 NPN, 1 PNP	100	50	2.2	47	80 @ 10mA, 5V	300 @ 250µA, 5mA	250	150	SOT-563, SOT-666	Active
DCX124EH-7	Diodes Inc.	1 NPN, 1 PNP	100	50	22	22	56 @ 5mA, 5V	300 @ 500µA, 10mA	250	150	SOT-563, SOT-666	Active
PEMD10,115	Nexperia	1 NPN, 1 PNP	100	50	2.2	47	100 @ 10mA, 5V	100 @ 250µA, 5mA	—	300	SOT-563, SOT-666	Not For New Designs
PEMH10,115	Nexperia	2 NPN	100	50	2.2	47	100 @ 100mA, 5V	100 @ 250µA, 5mA	—	300	SOT-563, SOT-666	Not For New Designs

Engineering Selection Recommendations

Direct Substitution (Identical Electrical and Mechanical Compatibility):

DCX123JH-7 (Diodes Incorporated) is the closest functional equivalent to RN1905FE,LF(CT. This part maintains identical base resistor (2.2kOhms) and emitter-base resistor (47kOhms) values, matching DC current gain specifications (80 @ 10mA, 5V), and identical saturation voltage characteristics (300mV @ 250µA, 5mA). The primary difference is transistor configuration (1 NPN + 1 PNP versus 2 NPN), which does not affect applications requiring only the NPN transistor function. DCX123JH-7 is actively produced and ROHS3 compliant. Inventory availability is 39,080 units.

Functional Equivalents with Resistor Variations:

EMH10T2R (Rohm Semiconductor) and DCX124EH-7 (Diodes Incorporated) both feature identical base and emitter-base resistor values (22kOhms each), resulting in different bias characteristics. These parts are suitable for applications where the modified bias network is acceptable. Both are actively produced with higher power ratings (150mW) and robust inventory levels.

DCX114YH-7 (Diodes Incorporated) provides an alternative with 10kOhms base resistor and 47kOhms emitter-base resistor, maintaining the 68 minimum DC current gain specification and identical saturation voltage performance. This configuration is suitable for circuits tolerating the modified base bias point.

Legacy Alternatives (Not Recommended for New Designs):

PEMD10,115 and PEMH10,115 (Nexperia USA Inc.) are marked "Not For New Designs" and should be avoided for new circuit development. These parts are retained in this reference for legacy system maintenance only. Both maintain the 2.2kOhms/47kOhms resistor configuration and offer superior saturation voltage performance (100mV) and higher power dissipation (300mW), but their obsolescence trajectory makes them unsuitable for new applications.

Compliance and Certification:

All recommended active-status substitutes maintain ROHS3 compliance and MSL 1 (unlimited) moisture sensitivity rating, ensuring compatibility with standard manufacturing and storage protocols.

Frequently Asked Questions (FAQ)

Q: Can DCX123JH-7 directly replace RN1905FE,LF(CT in all applications?

A: DCX123JH-7 is functionally equivalent for applications utilizing only the NPN transistor function. The primary difference is internal configuration (1 NPN + 1 PNP versus 2 NPN). If your circuit requires two independent NPN transistors, verify that the PNP transistor presence in DCX123JH-7 does not create unintended circuit interactions. For dual NPN-only requirements, PEMH10,115 maintains the 2 NPN configuration, though it is marked "Not For New Designs."

Q: What is the significance of the base resistor (R1) and emitter-base resistor (R2) values?

A: These integrated resistors establish the pre-bias network that determines the transistor's quiescent operating point. R1 (2.2kOhms in the main part) sets base bias current, while R2 (47kOhms) provides emitter-base bias stabilization. Parts with identical R1 and R2 values maintain identical bias characteristics. Parts with different resistor values (such as EMH10T2R with 22kOhms/22kOhms) produce different quiescent collector current and may require circuit re-evaluation.

Q: Why does DCX114EH-7 have lower DC current gain (30 @ 5mA, 5V) compared to RN1905FE,LF(CT (80 @ 10mA, 5V)?

A: DC current gain varies with measurement conditions (collector current and collector-emitter voltage). DCX114EH-7 is measured at 5mA collector current, while RN1905FE,LF(CT is measured at 10mA. The different measurement points reflect different transistor characteristics at those operating conditions. Selection depends on your circuit's actual operating point.

Q: Are all substitute parts available in the same package options?

A: Yes. All recommended substitutes are available in SOT-563 and SOT-666 surface mount packages, maintaining mechanical compatibility with RN1905FE,LF(CT PCB layouts.

Q: What is the difference between "Active" and "Not For New Designs" product status?

A: "Active" status indicates the manufacturer continues production and supports the part for new circuit designs. "Not For New Designs" indicates the manufacturer has discontinued active development but maintains limited production for legacy system support. New designs should utilize active-status parts to ensure long-term supply availability and manufacturer support.

Q: Can I use PEMD10,115 as a substitute despite its "Not For New Designs" status?

A: PEMD10,115 is electrically compatible and offers superior performance characteristics (100mV saturation voltage versus 300mV, 300mW power rating versus 100mW). However, its obsolescence trajectory makes it unsuitable for new product development. Use PEMD10,115 only for legacy system maintenance where supply is available and long-term availability is not a concern.

Q: How do I determine which substitute is appropriate for my specific application?

A: Evaluate your circuit requirements against three primary criteria: (1) transistor configuration requirement (2 NPN versus 1 NPN + 1 PNP), (2) bias point tolerance (identical resistor values versus alternative values), and (3) product lifecycle status (active production versus legacy support). Cross-reference your operating point (collector current and collector-emitter voltage) against the DC current gain and saturation voltage specifications provided in the parameter comparison table.

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