This continuity tester using 741 operational amplifier, operates as a differential amplifier.

A good application for this circuit would be to test welds made on a printed circuit board. It could be also used to test continuity of wires, connections, etc.

The Wheatstone bridge circuit

This circuit  was designed in 1833 by Samuel Hunter Christie (1784-1865). However, It was Mr. Charles Wheatstone who gave many uses to the Wheatstone bridge circuit when he discovered it in 1843.

Logic Probe using NOT Gates (Inverters)

This logic probe using NOT Gates is implemented with three NOT gates, one rectifier diode, two LEDs and two resistors.

How to test Diodes and how to test Transistors

Method to follow to to test a diode or transistor to know if they are working fine

How to Make a Diode Tester Circuit using 741?

This diode tester circuit checks if the diode is in good condition and also determines its polarity. To accomplish our goal, we use an 741 operational amplifier (IC1) configured as an oscillator.

How to Protect the 500 mA Fuse of a Multimeter?

It is very important to protect the 500 mA fuse of a Multimeter due to the high frequency that these are burned.

How to extend the voltage range of an analog Multimeter?

In order to extend the voltage range of an analog multimeter, a resistor is used. This resistor is placed in series with the multimeter.

Two Transistor Logic Probe

This Two Transistor Logic Probe is a very simple circuit that can be implemented using two NPN bipolar transistors (T1, T2) in a Darlington configuration.

Logic probe circuit with CD4001 IC

This logic probe circuit is useful for people who needs an instrument to measure the logic levels on digital circuits. This circuit is implemented with CMOS IC technology and is recommended for testing circuits using the same technology

Logic point using 7 segment display

This logic probe with 7 segment display is designed with TTL technology and does not use LEDs to display the high and low logic levels found in many of the logical probes on the market. The circuit shows the capital letter “H” when there is a logical “1” or the letter “L” when there is a logical “0”.