BAS21TA Equivalent & Substitute Parts

Part Overview

The BAS21TA is a high-speed switching diode manufactured by Diodes Incorporated, rated for 200 V DC reverse voltage and 200 mA average rectified current in a surface mount SOT-23-3 package. This component is classified as obsolete, which necessitates identification of active equivalent and substitute parts for ongoing design and procurement requirements. Equivalent parts maintain identical electrical and mechanical specifications, while substitute parts offer compatible performance within the same application envelope with potential variations in voltage rating, configuration, or manufacturer.

Key Parameters

Parameter	BAS21TA Value	Unit
Voltage - DC Reverse (Vr) (Max)	200	V
Current - Average Rectified (Io)	200	mA
Voltage - Forward (Vf) (Max) @ If	1.25 @ 200 mA	V
Reverse Recovery Time (trr)	50	ns
Current - Reverse Leakage @ Vr	100 nA @ 200 V	nA
Capacitance @ Vr, F	5 @ 0V, 1MHz	pF
Package / Case	TO-236-3, SC-59, SOT-23-3	—
Mounting Type	Surface Mount	—
Technology	Standard	—
Speed Classification	Small Signal ≤ 200mA (Io), Any Speed	—
Moisture Sensitivity Level (MSL)	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the BAS21TA is determined by equivalence in the following critical parameters: voltage rating (DC reverse), current rating (average rectified), forward voltage drop, reverse recovery time, package type, and mounting configuration. Parts are grouped into three categories based on electrical and physical compatibility:

Category 1: Direct Equivalents (200 V, 200 mA, Single Diode) Parts maintaining identical voltage and current ratings with single diode configuration in SOT-23-3 packaging. These parts are interchangeable at the circuit level with no design modification required.

Category 2: Higher Voltage Equivalents (250 V, 200 mA, Single Diode) Parts with elevated voltage rating (250 V) while maintaining 200 mA current rating and single diode configuration. These provide enhanced voltage margin and are backward-compatible with 200 V applications.

Category 3: Diode Array Configurations (200 V or 250 V, 200 mA per Diode) Parts with integrated diode pairs in common anode or common cathode configuration. These are suitable only for applications where the array topology matches the circuit design.

Substitution eligibility is determined by matching the following parameters: voltage rating (equal or higher), current rating (equal or higher), package type (SOT-23-3 / TO-236-3 / SC-59), mounting type (surface mount), and diode configuration (single diode or array as required).

Parameter Comparison

Part Number	Manufacturer	Vr (Max) [V]	Io [mA]	Vf (Max) @ If [V]	trr [ns]	Ir @ Vr [nA]	Package	Product Status	RoHS Status
BAS21TA	Diodes Incorporated	200	200	1.25 @ 200 mA	50	100 @ 200 V	SOT-23-3	Obsolete	Non-compliant
BAS21-7-F	Diodes Incorporated	200	200	1.25 @ 200 mA	50	100 @ 200 V	SOT-23-3	Active	ROHS3 Compliant
BAS21,215	Nexperia USA Inc.	200	200	1.25 @ 200 mA	50	100 @ 200 V	TO-236AB	Active	ROHS3 Compliant
BAS21,235	Nexperia USA Inc.	200	200	1.25 @ 200 mA	50	100 @ 200 V	TO-236AB	Active	ROHS3 Compliant
BAS21-TP	Micro Commercial Co	200	200	1.25 @ 200 mA	50	100 @ 200 V	SOT-23	Active	ROHS3 Compliant
BAS21A-TP	Micro Commercial Co	250	200	1.1 @ 100 mA	50	1000 @ 200 V	SOT-23	Active	ROHS3 Compliant
BAS21LT1G	onsemi	250	200	1.25 @ 200 mA	50	100 @ 200 V	SOT-23-3	Active	ROHS3 Compliant
BAS21LT3G	onsemi	250	200	1.25 @ 200 mA	50	100 @ 200 V	SOT-23-3	Active	ROHS3 Compliant
MMBD1504A	onsemi	200	200	1.1 @ 200 mA	50	10 @ 180 V	SOT-23-3	Active	ROHS3 Compliant

Engineering Selection Recommendations

For Direct Replacement (Identical Specifications): BAS21-7-F (Diodes Incorporated) is the primary direct equivalent, offering identical electrical parameters and active product status with ROHS3 compliance. BAS21,215 and BAS21,235 (Nexperia USA Inc.) provide equivalent performance with automotive-grade qualification (AEC-Q101) available for BAS21,215, suitable for applications requiring automotive reliability standards.

For Enhanced Voltage Margin: BAS21LT1G and BAS21LT3G (onsemi) provide 250 V reverse voltage rating while maintaining 200 mA current capacity and identical forward voltage characteristics. These parts are suitable for applications where increased voltage headroom is beneficial. Both are available in active status with ROHS3 compliance.

For General Purpose Applications: BAS21-TP (Micro Commercial Co) offers equivalent 200 V / 200 mA performance in active status with ROHS3 compliance and broad availability.

For Diode Array Configurations: MMBD1504A (onsemi) is a common cathode diode pair configuration rated 200 V / 200 mA per diode. This part is suitable only for circuit designs requiring integrated diode pair topology. BAS21A-TP (Micro Commercial Co) is a common anode diode pair rated 250 V / 200 mA per diode, applicable to designs requiring common anode configuration.

Compliance Considerations: All substitute parts listed are ROHS3 compliant and REACH unaffected, addressing environmental and regulatory requirements. The original BAS21TA is RoHS non-compliant; migration to any listed substitute ensures regulatory compliance for new designs and procurement.

Frequently Asked Questions (FAQ)

Q: Can BAS21-7-F directly replace BAS21TA without circuit modification? A: Yes. BAS21-7-F maintains identical electrical specifications (200 V, 200 mA, 1.25 V forward voltage, 50 ns recovery time) and package configuration (SOT-23-3). Direct substitution is valid at the component level.

Q: What is the difference between BAS21,215 and BAS21,235? A: Both parts are manufactured by Nexperia USA Inc. with identical electrical specifications. The primary difference is packaging: BAS21,215 is supplied in Cut Tape (CT) & Digi-Reel format, while BAS21,235 is supplied in Tape & Reel (TR) format. Electrical performance and compliance are equivalent.

Q: Why would I select BAS21LT1G or BAS21LT3G over BAS21-7-F? A: BAS21LT1G and BAS21LT3G offer 250 V reverse voltage rating compared to 200 V for BAS21-7-F. Selection depends on circuit voltage requirements. If the application operates at voltages approaching 200 V, the higher-rated parts provide additional safety margin. Both are active products with ROHS3 compliance.

Q: Can MMBD1504A be used in place of BAS21TA? A: MMBD1504A is a diode array with common cathode configuration, not a single diode. It is suitable only for applications where the circuit design specifically requires a diode pair with common cathode topology. Pin configuration and functional behavior differ from single-diode BAS21TA.

Q: What is the significance of the "Obsolete" status for BAS21TA? A: Obsolete status indicates the part is no longer manufactured or supported by the original supplier. For new designs, procurement of existing inventory, or long-term supply chain planning, selection of an active equivalent part is necessary. All substitute parts listed are in active production status.

Q: Are there temperature rating differences between substitute parts? A: Yes. BAS21-7-F and BAS21-TP specify operating junction temperature range of -65°C to 150°C. BAS21,215 and BAS21,235 specify maximum junction temperature of 150°C. BAS21LT1G and BAS21LT3G specify -55°C to 150°C. MMBD1504A specifies maximum junction temperature of 150°C. Circuit design must account for the applicable temperature range of the selected part.

Q: What does "1 Pair Common Anode" or "1 Pair Common Cathode" mean? A: These terms describe diode array configurations. Common Anode means both diodes share a single anode terminal; Common Cathode means both diodes share a single cathode terminal. Single-diode parts like BAS21TA have neither configuration. Array parts are suitable only for applications designed to use integrated diode pairs.

Q: Is BAS21A-TP compatible with BAS21TA? A: BAS21A-TP is a diode array with common anode configuration and 250 V rating, not a single diode. It is not a direct substitute for BAS21TA. Compatibility depends on whether the circuit design requires a diode pair or a single diode element.

Q: What packaging formats are available for substitute parts? A: Substitute parts are available in Cut Tape (CT) & Digi-Reel, Tape & Reel (TR), and bulk packaging formats. Selection depends on manufacturing process requirements and procurement volume. All parts maintain identical SOT-23-3 or TO-236-3 physical package dimensions suitable for surface mount assembly.

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