BAS21 Equivalent & Substitute Parts

Part Overview

The BAS21 is a small signal general-purpose diode manufactured by onsemi, rated for 250 V DC reverse voltage and 200 mA average rectified current in a surface mount SOT-23-3 package. This component is classified as obsolete in its original onsemi form, necessitating identification of active equivalent and substitute parts from alternative manufacturers and packaging variants that maintain electrical and mechanical compatibility for circuit applications requiring small signal switching or rectification functions.

Key Parameters

Parameter	Value	Unit
Voltage - DC Reverse (Vr) (Max)	250	V
Current - Average Rectified (Io)	200	mA
Voltage - Forward (Vf) (Max) @ If	1.25 @ 200	V @ mA
Reverse Recovery Time (trr)	50	ns
Current - Reverse Leakage @ Vr	100	nA @ 200 V
Capacitance @ Vr, F	5	pF @ 0V, 1MHz
Mounting Type	Surface Mount	—
Package / Case	TO-236-3, SC-59, SOT-23-3	—
Operating Temperature - Junction (Max)	150	°C
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the BAS21 is determined by strict adherence to the following electrical and mechanical parameters:

Primary Substitution Criteria:

Voltage - DC Reverse (Vr) (Max): 250 V or higher
Current - Average Rectified (Io): 200 mA
Voltage - Forward (Vf) (Max) @ If: 1.25 V @ 200 mA or lower
Reverse Recovery Time (trr): 50 ns
Current - Reverse Leakage @ Vr: 100 nA @ 200 V or lower
Capacitance @ Vr, F: 5 pF @ 0V, 1MHz or lower
Mounting Type: Surface Mount
Package / Case: TO-236-3, SC-59, SOT-23-3 or equivalent
Operating Temperature - Junction: 150°C (Max) or higher

Secondary Substitution Criteria (Acceptable Variations):

Reverse voltage rated at 200 V (lower than original 250 V specification) is acceptable for applications not requiring the full 250 V rating
Forward voltage measured at different test currents (e.g., 100 mA vs. 200 mA) is acceptable if the specified maximum does not exceed 1.25 V @ 200 mA
Reverse leakage current measured at different voltages is acceptable if the specified maximum does not exceed 100 nA @ 200 V
Capacitance measured at different voltages (e.g., 1 V vs. 0 V) is acceptable if the specified maximum does not exceed 5 pF @ 1MHz
Operating temperature range may extend below the minimum or above the maximum of the original specification

Non-Substitutable Variations:

Diode arrays (multiple diodes in single package) are not direct substitutes for single diode applications
Packages other than TO-236-3, SC-59, or SOT-23-3 are not substitutes
Reverse voltage ratings below 200 V are not substitutes for applications requiring 250 V rating

Parameter Comparison

Part Number	Manufacturer	Vr (Max) [V]	Io [mA]	Vf (Max) @ If [V @ mA]	trr [ns]	Ir @ Vr [nA @ V]	C @ Vr, F [pF @ V, MHz]	Package	Product Status
BAS21	onsemi	250	200	1.25 @ 200	50	100 @ 200	5 @ 0, 1	SOT-23-3	Obsolete
BAS21LT1G	onsemi	250	200	1.25 @ 200	50	100 @ 200	5 @ 0, 1	SOT-23-3	Active
BAS21	Taiwan Semiconductor Corporation	250	200	1.25 @ 200	50	100 @ 200	5 @ 1, 1	SOT-23-3	Active
BAS21,215	Nexperia USA Inc.	200	200	1.25 @ 200	50	100 @ 200	5 @ 0, 1	SOT-23-3	Active
BAS21,235	Nexperia USA Inc.	200	200	1.25 @ 200	50	100 @ 200	5 @ 0, 1	SOT-23-3	Active
BAS21-7-F	Diodes Incorporated	200	200	1.25 @ 200	50	100 @ 200	5 @ 0, 1	SOT-23-3	Active
BAS21-E3-08	Vishay General Semiconductor - Diodes Division	200	200	1.25 @ 200	50	100 @ 200	5 @ 0, 1	SOT-23-3	Active
BAS21-TP	Micro Commercial Co	200	200	1.25 @ 200	50	100 @ 200	5 @ 0, 1	SOT-23-3	Active
BAS21T-TP	Micro Commercial Co	250	200	1.25 @ 200	50	100 @ 250	5 @ 0, 1	SOT-523	Active
BAS21_R1_00001	Panjit International Inc.	200	200	1 @ 100	50	1 @ 200	1.5 @ 0, 1	SOT-23-3	Active

Engineering Selection Recommendations

Direct Equivalent (Full Specification Match):

BAS21LT1G (onsemi) is the direct active equivalent to the obsolete BAS21. This part maintains identical electrical specifications across all parameters and is supplied in the same SOT-23-3 package. BAS21LT1G is RoHS3 compliant and carries REACH Unaffected status, matching the regulatory profile of the original component.

Full-Specification Substitutes (250 V Rating):

BAS21 (Taiwan Semiconductor Corporation) and BAS21T-TP (Micro Commercial Co) maintain the full 250 V reverse voltage rating of the original BAS21. Both are active products with RoHS3 compliance. BAS21T-TP differs in package format (SOT-523 instead of SOT-23-3) and is not a direct mechanical substitute.

Reduced-Voltage Substitutes (200 V Rating):

BAS21,215, BAS21,235, BAS21-7-F, BAS21-E3-08, and BAS21-TP are active products rated for 200 V reverse voltage. These parts are suitable for applications where the circuit design does not require the full 250 V rating. All maintain 200 mA current rating, 50 ns reverse recovery time, and SOT-23-3 packaging. All are RoHS3 compliant.

Alternative Specification Substitute:

BAS21_R1_00001 (Panjit International Inc.) is rated for 200 V reverse voltage and differs in forward voltage specification (1 V @ 100 mA vs. 1.25 V @ 200 mA), reverse leakage current (1 µA @ 200 V vs. 100 nA @ 200 V), and junction capacitance (1.5 pF vs. 5 pF). This part is suitable only for applications where these parameter variations are acceptable.

Product Status Consideration:

All substitute parts listed are active products, eliminating obsolescence risk associated with the original BAS21 (onsemi) designation.

Frequently Asked Questions (FAQ)

Q: Can BAS21LT1G be used as a direct replacement for the obsolete BAS21 (onsemi)?

A: Yes. BAS21LT1G is manufactured by onsemi and maintains identical electrical and mechanical specifications. It is supplied in the same SOT-23-3 package and is an active product.

Q: What is the difference between BAS21 (onsemi) and BAS21 (Taiwan Semiconductor Corporation)?

A: Both are rated for 250 V reverse voltage and 200 mA current. The primary difference is manufacturer. Taiwan Semiconductor Corporation's BAS21 is an active product, while onsemi's BAS21 is obsolete. Capacitance measurement voltage differs (1 V vs. 0 V), but both specify 5 pF maximum at 1 MHz.

Q: Can I use a 200 V rated part in place of the 250 V rated BAS21?

A: Parts rated for 200 V reverse voltage (BAS21,215, BAS21,235, BAS21-7-F, BAS21-E3-08, BAS21-TP) are substitutes only for applications where the circuit design does not require 250 V blocking capability. Circuit analysis must confirm that maximum reverse voltage stress does not exceed 200 V.

Q: Is BAS21T-TP a suitable substitute?

A: BAS21T-TP maintains the 250 V rating and all electrical specifications of the original BAS21. However, it is supplied in SOT-523 package instead of SOT-23-3, making it unsuitable for applications requiring the standard SOT-23-3 footprint.

Q: What is the difference between BAS21_R1_00001 and other substitutes?

A: BAS21_R1_00001 differs in forward voltage (1 V @ 100 mA vs. 1.25 V @ 200 mA), reverse leakage current (1 µA @ 200 V vs. 100 nA @ 200 V), and junction capacitance (1.5 pF vs. 5 pF). These variations may affect circuit performance in sensitive applications. Use only where these parameter differences are acceptable.

Q: Are all listed substitutes RoHS3 compliant?

A: Yes. All active substitute parts listed carry RoHS3 compliance status. The original obsolete BAS21 (onsemi) does not specify RoHS status.

Q: What packaging options are available for BAS21 substitutes?

A: Most substitutes are supplied in SOT-23-3 (TO-236-3, SC-59) package. BAS21T-TP is supplied in SOT-523 package. Packaging format must match circuit board footprint requirements.

Q: Can BAS21A-TP be used as a substitute?

A: No. BAS21A-TP is a diode array (1 pair common anode configuration) and is not a direct substitute for single diode applications. It is a different product category.

Q: What is the moisture sensitivity level for BAS21 substitutes?

A: All listed substitutes specify MSL 1 (Unlimited), indicating no moisture sensitivity restrictions during storage or handling.

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