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A simple 5 Volt regulated PSU featuring overvoltage protection. The 5 volt regulated power supply for TTL and 74LS series integrated circuits, has to be very precise and tolerant of voltage transients. These IC's are easily damaged by short voltage spikes. A fuse will blow when its current rating is exceeded, but requires several hundred milliseconds to respond. This circuit will react in a few microseconds, triggered when the output voltage exceeds the limit of the zener diode. This circuit uses the crowbar method, where a thyristor is employed and short circuits the supply, causing the fuse to blow. This will take place in a few microseconds or less, and so offers much greater protection than an ordinary fuse. Circuit diagram: Logic PSU With Over-Voltage Protection Circuit Diagram If the output voltage exceed 5.6Volt, then the zener diode will conduct, switching on the thyristor (all in a few microseconds), the output voltage is therefore reduced to 0 volts and sensitive logic IC...

Bench power supplies aren’t really pieces of kit that get your pulse racing, they just sit there doing their job, in some cases giving gentle background heating to keep the lab warm in the winter and providing enough ballast to stop your bench wobbling about too much. The traditional bench top power supply always came with a sturdy handle on the top to give you a clue that inside is some serious ironwork and that this beast is going to be heavy. But that was all yesterday; buy a power supply today and it doesn’t look much different from any other piece of test gear; covered in buttons with a TFT display and the chances are you can wrap your hand around it and pick it up one-handed. That’s true of the HMC8043 three channel 100-watt bench power supply from Rohde & Schwarz I received for reviewing. [ ]