RN1905,LF Equivalent & Substitute Parts

Part Overview

The Toshiba RN1905,LF is a pre-biased dual NPN bipolar transistor (BJT) in a 6-TSSOP/SC-88/SOT-363 surface mount package. This component integrates two NPN transistors with internal base and emitter resistors, designed for switching and amplification applications requiring 50V collector-emitter breakdown voltage and 100mA maximum collector current. The RN1905,LF is classified as obsolete, necessitating identification of functionally equivalent active alternatives for new designs and ongoing production requirements.

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	mV @ 250µA, 5mA
Current - Collector Cutoff (Max)	500	nA
Frequency - Transition	250	MHz
Power - Max	200	mW
Mounting Type	Surface Mount	—
Package / Case	6-TSSOP, SC-88, SOT-363	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the RN1905,LF is determined by strict equivalence across the following critical parameters:

Primary Substitution Criteria:

Transistor configuration (2 NPN pre-biased dual or compatible mixed configuration)
Maximum collector current: 100mA
Collector-emitter breakdown voltage: 50V
Base resistor (R1): 2.2kOhms
Emitter-base resistor (R2): 47kOhms
DC current gain minimum: 80 @ specified test conditions
Surface mount package compatibility: 6-TSSOP, SC-88, SOT-363
Moisture sensitivity level: 1 (Unlimited)

Substitution Categories:

Direct Packaging Equivalent – Identical part number with different packaging format (tape & reel vs. bulk)
Functional Equivalent – Active Status – Different manufacturer, identical electrical specifications and package footprint, active product status
Similar Configuration – Mixed Transistor Type – Dual pre-biased transistor with one NPN and one PNP configuration, meeting all electrical parameters
Similar Configuration – Automotive Grade – Dual NPN pre-biased with AEC-Q101 qualification, meeting or exceeding electrical specifications
Similar Configuration – Enhanced Power Rating – Dual pre-biased transistor with higher power dissipation capability while maintaining core electrical parameters

Parts that deviate from the specified resistor values, transistor configuration, or electrical ratings are classified as similar but not direct substitutes and require circuit validation.

Parameter Comparison

Part Number	Manufacturer	Transistor Type	Ic Max (mA)	Vce Breakdown (V)	R1 (kOhms)	R2 (kOhms)	hFE Min @ Test	Vce Sat Max (mV)	Power Max (mW)	Package	Status
RN1905,LF	Toshiba	2 NPN	100	50	2.2	47	80 @ 10mA, 5V	300	200	SOT-363	Obsolete
RN1905,LF(CT	Toshiba	2 NPN	100	50	2.2	47	80 @ 10mA, 5V	300	200	SOT-363	Active
DCX123JU-7-F	Diodes Incorporated	1 NPN, 1 PNP	100	50	2.2	47	80 @ 10mA, 5V	300	200	SOT-363	Active
NSVMUN5235DW1T1G	onsemi	2 NPN	100	50	2.2	47	80 @ 5mA, 10V	250	385	SOT-363	Active
PUMD10,115	Nexperia	1 NPN, 1 PNP	100	50	2.2	47	100 @ 10mA, 5V	100	300	6-TSSOP	Active
PUMD10,135	Nexperia	1 NPN, 1 PNP	100	50	2.2	47	100 @ 10mA, 5V	100	300	6-TSSOP	Active
PUMD48,115	Nexperia	1 NPN, 1 PNP	100	50	2.2 / 47	47	80 @ 5mA, 5V / 100 @ 10mA, 5V	100 / 150	300	6-TSSOP	Active
PUMD48,165	Nexperia	1 NPN, 1 PNP	100	50	2.2 / 47	47	80 @ 5mA, 5V / 100 @ 10mA, 5V	100 / 150	300	6-TSSOP	Active
PUMH10Z	Nexperia	2 NPN	100	50	2.2	47	100 @ 10mA, 5V	100	300	6-TSSOP	Active
SMUN5231DW1T1G	onsemi	2 NPN	100	50	2.2	2.2	8 @ 5mA, 10V	250	250	SOT-363	Active
SMUN5235DW1T3G	onsemi	2 NPN	100	50	2.2	47	80 @ 5mA, 10V	250	187	SOT-363	Active

Engineering Selection Recommendations

Tier 1 – Direct Replacement (Identical Specifications)

RN1905,LF(CT (Toshiba) is the direct active equivalent of the obsolete RN1905,LF. This part maintains identical electrical specifications, internal resistor values, and package footprint. The only difference is packaging format (tape & reel vs. bulk). This part is recommended as the primary replacement for existing designs.

Tier 2 – Functional Equivalent (Active Alternatives)

SMUN5235DW1T3G (onsemi) and NSVMUN5235DW1T1G (onsemi) are dual NPN pre-biased transistors meeting all core electrical parameters. NSVMUN5235DW1T1G carries AEC-Q101 automotive qualification and is suitable for automotive and industrial applications. SMUN5235DW1T3G provides equivalent performance in a standard commercial grade. Both are available in high volume.

PUMH10Z (Nexperia) is a dual NPN pre-biased transistor with AEC-Q101 automotive qualification, enhanced DC current gain (100 vs. 80), and improved saturation voltage (100mV vs. 300mV). This part is suitable for applications requiring automotive-grade reliability.

Tier 3 – Mixed Configuration Alternatives (1 NPN, 1 PNP)

DCX123JU-7-F (Diodes Incorporated), PUMD10,115, PUMD10,135, PUMD48,115, and PUMD48,165 (Nexperia) feature mixed transistor configurations (one NPN, one PNP) with identical electrical parameters for the NPN section. These parts are suitable for applications requiring complementary transistor pairs within a single package. All are ROHS3 compliant and carry REACH Unaffected status.

Tier 4 – Similar Configuration with Parameter Deviations

SMUN5231DW1T1G (onsemi) is a dual NPN pre-biased transistor with identical base and emitter-base resistor values (2.2kOhms each), resulting in different DC current gain characteristics (8 vs. 80). This part is not recommended as a direct substitute without circuit validation.

Compliance and Certification:

All active substitute parts carry ROHS3 compliance. NSVMUN5235DW1T1G and PUMH10Z carry AEC-Q101 automotive qualification. All parts maintain MSL 1 (Unlimited) moisture sensitivity rating, matching the original specification.

Frequently Asked Questions (FAQ)

Q: Can I use RN1905,LF(CT as a direct replacement for RN1905,LF?

A: Yes. RN1905,LF(CT is the active equivalent of the obsolete RN1905,LF. Both parts have identical electrical specifications, internal resistor values (R1 = 2.2kOhms, R2 = 47kOhms), and package footprint (SOT-363). The only difference is packaging format (tape & reel). No circuit modifications are required.

Q: What is the difference between dual NPN and mixed NPN/PNP configurations?

A: Dual NPN parts (RN1905,LF, NSVMUN5235DW1T1G, PUMH10Z, SMUN5231DW1T1G, SMUN5235DW1T3G) contain two NPN transistors. Mixed configuration parts (DCX123JU-7-F, PUMD10,115, PUMD10,135, PUMD48,115, PUMD48,165) contain one NPN and one PNP transistor. Selection depends on circuit requirements. Dual NPN parts are direct substitutes for the RN1905,LF. Mixed configuration parts are suitable only if the circuit design accommodates a complementary transistor pair.

Q: Are all substitute parts pin-compatible with RN1905,LF?

A: All substitute parts use the 6-TSSOP/SC-88/SOT-363 package family, which shares the same 6-pin footprint. However, internal pin assignments may differ between dual NPN and mixed NPN/PNP configurations. Verify pin-to-function mapping in the respective datasheets before substitution.

Q: What is the significance of the internal resistor values (R1 and R2)?

A: The internal base resistor (R1) and emitter-base resistor (R2) determine the transistor's switching speed and biasing characteristics. The RN1905,LF specifies R1 = 2.2kOhms and R2 = 47kOhms. Substitute parts must maintain these values for functional equivalence. SMUN5231DW1T1G deviates with R2 = 2.2kOhms and is not a direct substitute.

Q: Which substitute parts are suitable for automotive applications?

A: NSVMUN5235DW1T1G and PUMH10Z carry AEC-Q101 automotive qualification. These parts are suitable for automotive and industrial applications requiring enhanced reliability and temperature stability. Both maintain the core electrical specifications of the RN1905,LF.

Q: What is the difference between PUMD10,115 and PUMD10,135?

A: Both parts are identical in electrical specifications and package. The difference is in the current collector cutoff specification: PUMD10,115 specifies 100nA (ICBO), while PUMD10,135 specifies 1µA. Both are functionally equivalent for most applications. Selection depends on leakage current requirements.

Q: Can I substitute SMUN5235DW1T3G for RN1905,LF without circuit modifications?

A: SMUN5235DW1T3G is functionally equivalent in terms of transistor type (2 NPN), electrical ratings (100mA, 50V), and internal resistor values (R1 = 2.2kOhms, R2 = 47kOhms). However, it has lower power dissipation (187mW vs. 200mW) and different saturation voltage characteristics (250mV vs. 300mV). Verify thermal and switching performance in your specific application before substitution.

Q: What does ROHS3 compliance mean?

A: ROHS3 compliance indicates the part meets the Restriction of Hazardous Substances Directive 3, restricting the use of lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls, and polybrominated diphenyl ethers. All active substitute parts listed are ROHS3 compliant.

Q: Are there any inventory considerations when selecting a substitute?

A: Inventory availability varies by part and supplier. RN1905,LF(CT (Toshiba) has 5,568 units in stock. SMUN5235DW1T3G (onsemi) has 11,125 units. PUMH10Z (Nexperia) has 10,426 units. Verify current inventory with your supplier before finalizing part selection for production requirements.

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