IC Tester

Although ICs 741 and timer 555 are rare and expensive these ICs  are frequently used ICs even by an average hobbyist and electronics students. They are very versatile and damage resistant too. Therefore we have designed the IC tester for timer IC 555 And Op-Amp IC 741

The tester described here test both the ICs [Timer 555 and Op-Amp 741] instantly. The circuit here uses only a few resistors, switches, sockets and capacitors which cost around $3 including the PCB and the 7-segment display. The tester we design is equally useful for a factory and the student of electronics.


IC1 555 Timer
IC2 741 Op-Amp
D1,D2  5mm LEDs  [Light Emitting Diode]
DIS1 FND507/LT542 Common Anode Display
Resistors  (all 0.25 watt 5% carbon)
R1 12 kilohm
R2 68 kilohm
R3,R4 10 kilohm
R5 TO R12 1 kilohm
C1 5μF, 16V electrolytic
C2 47μF, 10V electrolytic
S1 On/Off toggle Switch
S2 DPDT miniature switch for mounting on PCB
BATT 9-Volt, battery
OTHRES IC socket, PCB, connecting wires, enclosure, hardware etc

 Circuit Description

Form the circuit diagram it is clear that the heart of this tester is the astable multi vibrator formed around 1C 555 which is  approximately 2 Hz frequency. So, the output LED D1 (connected through link a and b snow in the circuit)  blinks at a rate of 2 Hz if the IC 555 inserted in the socket works well.This output at pin 3 of IC 555 is also given through a DPDT (Double Pole Double Throw switch) to the pins2 and pin3 of IC 741 op-amp. The switch S2 selects the inverting or non-inverting input of the IC 741 . In this way the LED D2 ( connected through link c and d snow in the circuit) also blinks at of 2Hz rate if the IC 741 inserted is OK. If S2 selects inverting mode, then D1 and D2 blink alternately and if S2 selects non-inverting mode then D1 and D2 blink simultaneously. You may use 3V to 12V  DC supply voltage safely. However, 9V DC is recommended.

More About circuit

As an interesting feature which gives a digital display without any confusion, you may use a common anode seven segment display. With op-amp IC 741 in inverting mode, the display shows 7 and 5 alternately. In the non-inverting mode it shows 9 and 0 alternately.

Common Anode display Configuration for connecting Display with circuit ( Please connect the A , C and B or D to the corresponding  point in the circuit.:

common anode connection

Both, the two LEDs and digital display options are given circuit diagram. You can also use a common anode display having a damaged decimal dot and / or segment ‘e’ which are not used here

Common Cathode display Configuration for connecting Display with circuit ( Please connect the A and C  to the corresponding  point in the circuit.:

common anode connection

You may also use a common cathode display here by just interchanging the connections of common cathode from positive to the negative of the supply on the PCB near the switch S2. Similarly, interchange the connections of R7 and R8 from negative to positive of the supply.

PCB Layout


It has been noted that when both IC 741 and 555 are faulty or in non-operating condition, the display shows 7 (but there is no change in the display while changing the switch S2), and when IC 555 is working and 741 is in non-operating condition the display shows 5 and 7 alternately and when IC 555 is not working but 741 is alright, then display shows 7 in inverting mode and 7 in non-inverting mode, but does not flash.



Related Project

  1. Versatile Digital Tester digital tester for detection of condition of the components as well as nature of defect
  2. Noise Meter measure the level of noise indicating by LED, warning alarm after crossing the safe level
  3. Test a Diode | Zener Diode tests the diode as well as zener diode 
  4. Ohm Meter measuring the low resistance range form 0 to 1 and and 0 to 10.
  5. Timer IC Tester check IC NE555 whether it have fault or not

Have You Say!

Please leave your Suggestions , Feedback , queries and comments through the comment section below. We will do our best to reply to your comment within 12-24 hours.
P.S. Emails regarding project helps will be strictly ignored ; so please use this Comment form instead.


  1. intresting but can u give me a hint on how to connect 7 segment display to ic 741 to read out temperature instead of a multimeter?

    • Yeah As shown on the image above first of all connect registers to the required pins of Seven Segmented Display and then connect the points A,C, (B or D) to the A,C, (B or D) of the circuit if it is a common anode Display and to point A and C of the circuit if it is a common Cathode display.

  2. Its interesting and informative. if more information regarding the connection using LED display would made still more better.

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