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 extend the voltage range of an analog Multimeter? In order to extend the voltage range, a resistor is placed in series with the multimeter. Calculation example.

Logic probe circuit with CD4001 IC. This circuit is implemented with CMOS IC technology and is recommended for testing circuits using the same technology

How to measure the resistance of a delicate or sensitive component?

There is a special way of resistance measurement when the component to be measured is very sensitive or delicate.

How to Measure Beta of a Transistor? (β / hfe of transistor)

The beta (β) is a characteristic of each transistor. This feature is found in the NTE, ECG manuals, etc. These manuals have a minimum or approximate values of the real values. This means that we do not know the real value of the transistor.

How to protect the 500mA Fuse of a Multimeter?

A very simple circuit that protect the 500mA fuse of a multimeter, due to the high frequency that these are burned.

Continuity tester using 741 operational amplifier that operates as a differential amplifier.

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

Measuring Low or very low resistances

There are cases where the resistance is too low and a direct use of the ohmmeter is not practical. So a special method is needed

This Electric Current Flow Indicator gives a visual indication that there is a current flow. Possible applications for this small circuit may be: a battery charger, a voltage power source, etc.

In order to achieve our objective we place 3 rectifier diodes in series, which in turn are in series with the load / battery.

Op Amp Tester Circuit Diagram

Very simple circuit to test 741 op amp or another IC with the same pin configuration. Circuit working explanation

555 IC Tester Circuit (PCB)

This 555 IC tester circuit, allows us to make sure that this integrated circuit works properly. This same test can be achieved by operating the 555 as astable multivibrator, but this test does not allow
to observe its operation in detail.

What is the reason to use an audible logic probe?

Many logic probes use LEDs to visually indicate the logic state of the point under test. This causes the user to have to see the point under test and the LED at the same time.