Product Overview
Unidirectional 78V Standoff TVS Clamping Diode in DO-41 Axial Package
Condition
New old stock (NOS), unused surplus in clean physical condition. Molded black cylindrical DO-41 package with straight, uncut axial wire leads. Diode bodies display the Motorola circled-M logo, partial SA series marking, and a silver cathode polarity band. Units are sold individually.
Ships same or next business day from our Idaho warehouse. Honest pricing, no nonsense.
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Product Overview
The Motorola SA78A is an axial-leaded silicon transient voltage suppressor (TVS) designed to protect sensitive semiconductor devices against high-energy voltage transients. Built in a compact molded plastic DO-41 package, this unidirectional diode provides rapid clamping action with a 500-watt peak pulse power dissipation rating at a 10/1000 microsecond waveform.
Key Features
- Reverse standoff voltage (VRWM): 78 V
- Breakdown voltage (VBR): 86.7 V minimum, 95.8 V maximum at 1 mA test current
- Maximum clamping voltage (VRSM): 126 V at 4.0 A peak pulse current
- Peak pulse power dissipation: 500 W (10/1000 µs waveform)
- Steady-state power dissipation: 3.0 W maximum
- Unidirectional polarity indicated by silver cathode band
- Through-hole DO-41 (Case 59-04) axial-leaded package
Applications
- Soldering replacement clamping diodes into industrial power supply rails to suppress inductive switching transients
- Bench-building custom test fixtures and breadboard prototypes requiring overvoltage spike protection
- Repairing legacy analog telemetry, telecommunications lines, and motor drive interface boards
- Adding front-end surge suppression to maker electronics, robotics controllers, and amateur radio transceivers
Frequently Asked Questions
Is this diode unidirectional or bidirectional?
This is a unidirectional diode. The silver band printed around the black molded body marks the cathode lead.
What package type does the SA78A use?
The SA78A is housed in a standard through-hole axial DO-41 plastic package (Motorola Case 59-04) with solder-plated leads.
Can I buy just a few diodes, or do I have to order a full reel?
You can purchase the exact quantity needed for your bench or repair without buying full production reels or dealing with distributor minimums. For larger projects, more pieces cost less each, and the price-break table on this page shows what each quantity costs. Shipping is $8 flat rate, free once the order passes $28, and orders leave the Idaho warehouse the same or next business day.
A TVS diode spends its entire working life waiting in total silence, hoping it never has to do its job. When an unexpected spike hits the rail, this part clamps down in nanoseconds so the rest of your board lives to see tomorrow.
