1N4705-TP Zener Diode Equivalent & Substitute Parts

Part Overview

The 1N4705-TP is an 18 V, 500 mW Zener diode in DO-35 axial package manufactured by Micro Commercial Co. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The 1N4705-TP operates as a voltage regulation and transient protection element in electronic circuits requiring 18 V reference voltage with moderate power dissipation capability.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	18	V
Tolerance	±5%	%
Power - Max	500	mW
Current - Reverse Leakage @ Vr	50	nA @ 13.6 V
Voltage - Forward (Vf) (Max) @ If	1.5	V @ 100 mA
Operating Temperature	200	°C (TJ)
Mounting Type	Through Hole	-
Package / Case	DO-204AH, DO-35, Axial	-
RoHS Status	ROHS3 Compliant	-

Substitute Part Grouping Explanation

Substitution of the 1N4705-TP is determined by the following critical parameters:

Primary Substitution Criteria:

Voltage - Zener (Nom): 18 V (exact match required)
Tolerance: ±5% (exact match required)
Power - Max: 500 mW (exact match required)
Package / Case: DO-35 axial through-hole (exact match required)
RoHS Status: ROHS3 Compliant (compliance requirement)

Substitute Classification:

Direct Substitutes maintain identical electrical specifications and packaging. These parts are functionally interchangeable with the 1N4705-TP:

1N4705 TR PBFREE (Central Semiconductor Corp)
1N5248B TR PBFREE (Central Semiconductor Corp)
1N5248B BK PBFREE (Central Semiconductor Corp)

Similar Substitutes meet all critical electrical and mechanical parameters but may have enhanced specifications, automotive qualification, or different impedance characteristics:

1N5248B-TAP (Vishay General Semiconductor - Diodes Division)
1N5248B-TR (Vishay General Semiconductor - Diodes Division)
BZX55C18-TR (Vishay General Semiconductor - Diodes Division)

Non-Equivalent Parts do not meet substitution criteria:

1N5254B-TAP (27 V Zener voltage; incompatible with 18 V requirement)

Parameter Comparison

Part Number	Manufacturer	Vz (Nom)	Tolerance	Power Max	Vf (Max) @ If	Ir @ Vr	Package	Status	RoHS
1N4705-TP	Micro Commercial Co	18 V	±5%	500 mW	1.5 V @ 100 mA	50 nA @ 13.6 V	DO-35	Obsolete	ROHS3
1N4705 TR PBFREE	Central Semiconductor Corp	18 V	±5%	500 mW	1.5 V @ 100 mA	50 nA @ 13.6 V	DO-35	Active	ROHS3
1N5248B TR PBFREE	Central Semiconductor Corp	18 V	±5%	500 mW	1.1 V @ 200 mA	100 nA @ 14 V	DO-35	Active	ROHS3
1N5248B BK PBFREE	Central Semiconductor Corp	18 V	±5%	500 mW	1.1 V @ 200 mA	100 nA @ 14 V	DO-35	Active	ROHS3
1N5248B-TAP	Vishay General Semiconductor	18 V	±5%	500 mW	1.1 V @ 200 mA	100 nA @ 14 V	DO-35	Active	ROHS3
1N5248B-TR	Vishay General Semiconductor	18 V	±5%	500 mW	1.1 V @ 200 mA	100 nA @ 14 V	DO-35	Active	ROHS3
BZX55C18-TR	Vishay General Semiconductor	18 V	±5%	500 mW	1.5 V @ 200 mA	100 nA @ 13 V	DO-35	Active	ROHS3
1N5254B-TAP	Vishay General Semiconductor	27 V	±5%	500 mW	1.1 V @ 200 mA	100 nA @ 21 V	DO-35	Active	ROHS3

Engineering Selection Recommendations

For Direct Replacement (Obsolete Part Substitution):

The 1N4705 TR PBFREE from Central Semiconductor Corp is the primary direct substitute. This part maintains identical electrical specifications and packaging while offering active product status and ROHS3 compliance. The part is available in Tape & Reel packaging with 849 units in stock.

For Active Production Designs:

The 1N5248B series (available from Central Semiconductor Corp and Vishay General Semiconductor) provides enhanced specifications suitable for new designs. These parts maintain the 18 V nominal Zener voltage and 500 mW power rating while offering improved forward voltage characteristics (1.1 V @ 200 mA versus 1.5 V @ 100 mA) and lower impedance (21 Ohms maximum). All variants are ROHS3 compliant with active product status.

For Automotive Applications:

The 1N5248B-TAP and BZX55C18-TR from Vishay General Semiconductor include AEC-Q101 automotive qualification. These parts are suitable for applications requiring automotive-grade reliability and traceability. The 1N5248B-TAP offers the lowest impedance specification (21 Ohms) among qualified options.

Inventory Availability Consideration:

The BZX55C18-TR offers the highest inventory availability (105,254 units) among all substitute options, supporting high-volume procurement requirements.

Non-Equivalent Parts:

The 1N5254B-TAP operates at 27 V nominal Zener voltage and is not suitable for 18 V circuit applications. This part does not meet substitution criteria.

Frequently Asked Questions (FAQ)

Q: Can the 1N4705-TP be replaced with the 1N5254B-TAP?

A: No. The 1N5254B-TAP is rated for 27 V nominal Zener voltage, while the 1N4705-TP operates at 18 V. The voltage mismatch makes this substitution incompatible with the original circuit design.

Q: What is the difference between 1N5248B TR PBFREE and 1N5248B BK PBFREE?

A: Both parts have identical electrical specifications and DO-35 packaging. The primary difference is packaging format: TR PBFREE is supplied in Cut Tape (CT) format with 9,573 units in stock, while BK PBFREE is supplied in Bulk format with 905 units in stock. Selection depends on procurement and assembly requirements.

Q: Are the Central Semiconductor Corp and Vishay General Semiconductor versions interchangeable?

A: Yes, for the 1N5248B series. Both manufacturers produce parts with identical 18 V nominal Zener voltage, ±5% tolerance, and 500 mW power rating in DO-35 packaging. The Vishay versions include automotive qualification (AEC-Q101) and may be preferred for automotive applications.

Q: Does the 1N4705 TR PBFREE maintain the same operating temperature as the original 1N4705-TP?

A: The 1N4705 TR PBFREE extends the operating temperature range to -65°C ~ 200°C (TJ), compared to the 1N4705-TP specification of 200°C (TJ). This represents an enhancement in low-temperature capability while maintaining the maximum temperature rating.

Q: What does the impedance (Zzt) parameter indicate?

A: Impedance (Zzt) represents the dynamic impedance of the Zener diode at the nominal Zener voltage. Lower impedance values indicate better voltage regulation characteristics. The 1N5248B series (21 Ohms) offers superior regulation compared to the BZX55C18-TR (50 Ohms).

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All substitute parts listed in this reference maintain ROHS3 compliance, meeting environmental and regulatory requirements equivalent to the original 1N4705-TP.

Q: What packaging options are available for the 1N5248B?

A: The 1N5248B is available in three packaging formats: Cut Tape (CT) as 1N5248B TR PBFREE, Bulk as 1N5248B BK PBFREE, and Cut Tape (CT) as 1N5248B-TAP from Vishay. Selection depends on assembly process requirements and procurement volume.

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