RN4985,LF(CT Pre-Biased Bipolar Transistor Equivalent & Substitute Parts

Part Overview

The RN4985,LF(CT is a pre-biased dual bipolar transistor (1 NPN, 1 PNP) manufactured by Toshiba Semiconductor and Storage. This surface mount component operates at 50V maximum collector-emitter breakdown voltage with 100mA maximum collector current and 200mW power dissipation. The device integrates internal base and emitter-base resistors (2.2kOhms and 47kOhms respectively) for simplified circuit design. The RN4985,LF(CT is classified as Active product status and is ROHS3 compliant with unlimited moisture sensitivity level (MSL 1). Equivalent and substitute parts are necessary when the primary part experiences supply constraints, extended lead times, or when design flexibility across multiple manufacturers is required for production optimization.

Key Parameters

Parameter	Value	Unit
Transistor Type	1 NPN, 1 PNP - 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
Power - Max	200	mW
Frequency - Transition	250, 200	MHz
Package / Case	6-TSSOP, SC-88, SOT-363	—
Mounting Type	Surface Mount	—
RoHS Status	ROHS3 Compliant	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the RN4985,LF(CT is determined by strict electrical and mechanical parameter matching. The critical parameters that define substitutability are:

Mandatory Matching Parameters:

Transistor Type: 1 NPN, 1 PNP - Pre-Biased (Dual) configuration
Maximum Collector Current (Ic): 100mA
Maximum Collector-Emitter Breakdown Voltage: 50V
Base Resistor (R1): 2.2kOhms
Emitter-Base Resistor (R2): 47kOhms
Minimum DC Current Gain (hFE): 80 @ 10mA, 5V
Maximum Vce Saturation: 300mV @ 250µA, 5mA
Package compatibility: 6-TSSOP, SC-88, SOT-363
Surface Mount technology
RoHS3 compliance

Flexible Parameters (within acceptable ranges):

Power dissipation: 200mW or higher
Transition frequency: 250MHz or higher
Collector cutoff current (ICBO): variations acceptable
Specific manufacturer implementation

Substitute parts are grouped into two categories:

Category A - Direct Electrical Equivalents (1 NPN, 1 PNP): Parts maintaining identical transistor configuration with matching base and emitter-base resistor values.

Category B - Functional Alternatives (2 NPN configuration): Parts with dual NPN transistors instead of NPN/PNP combination. These require circuit topology evaluation but maintain core electrical parameters.

Parameter Comparison

Parameter	RN4985,LF(CT	DCX123JU-7-F	DCX123JUQ-7-F	DDC123JU-7-F	MUN5235DW1T1G	MUN5335DW1T1G	PUMD10,115	PUMD10,125	PUMD10,135	PUMD48,115	PUMD48,125
Manufacturer	Toshiba	Diodes Inc.	Diodes Inc.	Diodes Inc.	onsemi	onsemi	Nexperia	Nexperia	Nexperia	Nexperia	Nexperia
Transistor Type	1 NPN, 1 PNP	1 NPN, 1 PNP	1 NPN, 1 PNP	2 NPN	2 NPN	1 NPN, 1 PNP	1 NPN, 1 PNP	1 NPN, 1 PNP	1 NPN, 1 PNP	1 NPN, 1 PNP	1 NPN, 1 PNP
Ic (Max)	100	100	100	100	100	100	100	100	100	100	100
Vce Breakdown (Max)	50	50	50	50	50	50	50	50	50	50	50
R1 (Base)	2.2k	2.2k	2.2k	2.2k	2.2k	2.2k	2.2k	2.2k	2.2k	2.2k / 47k	2.2k / 47k
R2 (Emitter-Base)	47k	47k	47k	47k	47k	47k	47k	47k	47k	47k	47k
hFE (Min) @ Ic, Vce	80 @ 10mA, 5V	80 @ 10mA, 5V	80 @ 10mA, 5V	80 @ 10mA, 5V	80 @ 5mA, 10V	80 @ 5mA, 10V	100 @ 10mA, 5V	100 @ 10mA, 5V	100 @ 10mA, 5V	80 @ 5mA, 5V / 100 @ 10mA, 5V	80 @ 5mA, 5V / 100 @ 10mA, 5V
Vce Sat (Max) @ Ib, Ic	300mV @ 250µA, 5mA	300mV @ 250µA, 5mA	300mV @ 250µA, 5mA	300mV @ 250µA, 5mA	250mV @ 300µA, 10mA	250mV @ 300µA, 10mA	100mV @ 250µA, 5mA	100mV @ 250µA, 5mA	100mV @ 250µA, 5mA	100mV @ 250µA, 5mA / 150mV @ 500µA, 10mA	100mV @ 250µA, 5mA / 150mV @ 500µA, 10mA
Power (Max)	200	200	200	200	250	250	300	200	300	300	300
Frequency - Transition	250, 200	250	250	250	—	—	230	—	—	—	—
Package	SOT-363	SOT-363	SOT-363	SOT-363	SC-88/SOT-363	SC-88/SOT-363	6-TSSOP	6-TSSOP	6-TSSOP	6-TSSOP	6-TSSOP
RoHS Status	ROHS3	ROHS3	ROHS3	ROHS3	ROHS3	ROHS3	ROHS3	ROHS3	ROHS3	ROHS3	ROHS3
MSL	1	1	1	1	1	1	1	1	1	1	1

Engineering Selection Recommendations

Primary Substitutes (Direct Equivalents - 1 NPN, 1 PNP Configuration):

DCX123JU-7-F (Diodes Incorporated) - Identical electrical specifications with matching base and emitter-base resistor values. SOT-363 package. Active product status. ROHS3 compliant. Suitable for direct replacement in all applications.
DCX123JUQ-7-F (Diodes Incorporated) - Functionally equivalent with automotive qualification (AEC-Q101). SOT-363 package. Active product status. ROHS3 compliant. Recommended for automotive-grade applications requiring enhanced reliability documentation.
MUN5335DW1T1G (onsemi) - Maintains 1 NPN, 1 PNP configuration with matching resistor values. SC-88/SOT-363 package compatibility. Active product status. ROHS3 compliant. Higher power rating (250mW) provides design margin.
PUMD10,115 (Nexperia) - 1 NPN, 1 PNP configuration with matching resistor values. 6-TSSOP package. Active product status. ROHS3 compliant. Higher power rating (300mW) and improved saturation characteristics (100mV vs 300mV).
PUMD10,125 (Nexperia) - 1 NPN, 1 PNP configuration with matching resistor values. 6-TSSOP package. Active product status. ROHS3 compliant. Maintains 200mW power rating with improved saturation performance.
PUMD10,135 (Nexperia) - 1 NPN, 1 PNP configuration with matching resistor values. 6-TSSOP package. Active product status. ROHS3 compliant. Higher power rating (300mW) for thermal margin applications.
PUMD48,115 (Nexperia) - 1 NPN, 1 PNP configuration with dual base resistor options (2.2kOhms and 47kOhms). 6-TSSOP package. Active product status. ROHS3 compliant. Flexible biasing network design.
PUMD48,125 (Nexperia) - 1 NPN, 1 PNP configuration with dual base resistor options. 6-TSSOP package. Active product status. ROHS3 compliant. Flexible biasing network design with 300mW power rating.

Secondary Substitutes (Functional Alternatives - 2 NPN Configuration):

DDC123JU-7-F (Diodes Incorporated) - Dual NPN configuration instead of NPN/PNP. Matching base and emitter-base resistor values. SOT-363 package. Active product status. ROHS3 compliant. Requires circuit topology evaluation for PNP replacement strategy.
MUN5235DW1T1G (onsemi) - Dual NPN configuration. Matching resistor values. SC-88/SOT-363 package. Active product status. ROHS3 compliant. Higher power rating (250mW). Requires circuit redesign for PNP functionality.

Compliance and Regulatory Status:

All substitute parts maintain ROHS3 compliance and unlimited moisture sensitivity level (MSL 1), ensuring compatibility with standard manufacturing and storage conditions. All parts are classified as Active product status, confirming ongoing manufacturer support and availability.

Frequently Asked Questions (FAQ)

Q1: Can DCX123JU-7-F directly replace RN4985,LF(CT without circuit modification?

A: Yes. DCX123JU-7-F maintains identical transistor configuration (1 NPN, 1 PNP), matching base resistor (2.2kOhms), emitter-base resistor (47kOhms), and electrical specifications. Both use SOT-363 packaging. Direct substitution is supported.

Q2: What is the difference between SOT-363 and 6-TSSOP packages?

A: SOT-363 and 6-TSSOP are equivalent package designations for the same physical form factor. Both refer to a 6-pin surface mount package with identical pin spacing and dimensions. Parts specified as either package type are mechanically interchangeable.

Q3: Why would PUMD10,115 be preferred over the original RN4985,LF(CT?

A: PUMD10,115 offers improved performance characteristics: higher power dissipation (300mW vs 200mW), lower saturation voltage (100mV vs 300mV), and higher transition frequency (230MHz). These parameters provide design margin and enhanced switching performance while maintaining full electrical compatibility.

Q4: Can DDC123JU-7-F (dual NPN) replace RN4985,LF(CT (NPN/PNP) in all circuits?

A: No. DDC123JU-7-F contains two NPN transistors instead of one NPN and one PNP. Circuits requiring PNP functionality must be redesigned using external PNP transistors or alternative topologies. Electrical parameters for the NPN section are compatible.

Q5: Are automotive-qualified parts (DCX123JUQ-7-F) required for all applications?

A: Automotive qualification (AEC-Q101) is required only for automotive applications. For industrial, consumer, or general-purpose applications, standard-grade equivalents (DCX123JU-7-F) provide identical electrical performance at lower cost.

Q6: What does the PUMD48 series offer compared to PUMD10?

A: PUMD48,115 and PUMD48,125 provide dual base resistor options (2.2kOhms and 47kOhms), enabling flexible biasing network design. PUMD10 series offers single base resistor configuration (2.2kOhms). Both maintain identical emitter-base resistor (47kOhms) and core electrical specifications.

Q7: How do transition frequency differences affect substitution?

A: Transition frequency (fT) indicates maximum switching speed capability. RN4985,LF(CT specifies 250MHz and 200MHz. Substitutes with equal or higher transition frequency (DCX123JU-7-F at 250MHz, PUMD10,115 at 230MHz) are fully compatible. Parts without specified transition frequency are acceptable if other electrical parameters match.

Q8: What is the significance of collector cutoff current (ICBO) variations?

A: ICBO represents leakage current in the off state. RN4985,LF(CT specifies 100µA maximum. Substitutes with lower ICBO values (DCX123JU-7-F at 500nA, PUMD10,115 at 100nA) provide improved performance and lower power consumption. Higher ICBO values are not acceptable.

Q9: Are all listed substitutes in active production?

A: Yes. All substitute parts listed are classified as Active product status, confirming ongoing manufacturer production and support. This ensures long-term availability and supply chain stability.

Q10: What packaging considerations apply when switching between manufacturers?

A: All listed substitutes use compatible surface mount packages (SOT-363 or 6-TSSOP). Pin configurations are identical. PCB footprints and reflow soldering profiles are interchangeable. No PCB redesign is required for package compatibility.

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