Transistor Overvoltage Crowbar Protector

This is a transistor crowbar circuit for overvoltage protection. This circuit is used to protect any devices, when the overvoltage occurs. This circuit consist of diode, transistor, and resistor, and a fuse.  The device that needs to be protected should be connected in parallel with the transistor. The 1N87 diode cut off the transistor across supply line until overvoltage occur. […]

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Battery Tester/Indicator/Monitor

This is a battery tester circuit.This circuit is used to indicate whether the level of a battery voltage is  normal, under-voltage, or over-voltage, very useful to make sure an electrical system will works properly. This circuit displays three classes of voltage level condition: high, low and normal. This circuit defines high level voltage if the voltage is more than 15 […]

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5V FET Voltage Regulator and How It Works

Using a FET and two additional transistors (cascaded to improve the gain), a 5V FET voltage regulator can be formed. The additional Tr2 and Tr3 transistors will improve the output current handling and decrease the output impedance. The output voltage deviate only 0.1V for load current change as high as 60 mA which is caused by load resistance changes that […]

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