The Semiconductor Tester is used to test diodes, transistors and also to test the continuity. Many times it is required to test the semiconducting components. This is a simple and inexpensive tester, used to test virtually any kind of semiconducting components such as switching diodes, transistors, power transistors etc. It is also useful in finding functional, short circuited and internally open devices in semiconductor batches.
About the Circuit :

• The circuit is build around IC1 which consists of four NAND gates. One of the gate from an RC oscillator. The oscillator signal is buffered and made available in true and inverted form by the three remaining gates.
• The two color LEDs (Red and Green) indicates the direction of the current flow or the device under test. Resistor R1 functions as a current limiter.
• The signals at the input and the output of IC1 are applied to a pair of test probes, a two-terminal test socket for diodes, and a three-terminal transistor. The base current for the transistor on test (TUT) can be set with preset P1.
• Only one LED lights when component is functional. When the component is internally open, no LED lights. The semiconductor with internal short circuit is easily recognized by the glowing of both the LEDs with equal intensity.

The testing procedure for diodes, transistors and continuity testing is as follows :

• Transistor Testing : Transistor to be tested must be connected with the base, emitter and collector pins to the indicated socket terminal. If Red LED glows then transistor is PNP type. And if green LED glows then it is NPN type. If transistor is not functional no LEDs glows and if it is short both LEDs glows with equal intensity.
• Diode Testing : With this tester we can test the cathode and anode terminals of a Diode. As above place DUT in the indicated socket. If Red LED glows then the terminal, which is connected to TP1 is cathode and other is anode. If Green LED glows then the terminal connected to TP1 is anode and other is cathode. Testing of functionality and short circuiting is same as described in transistor testing.
• Continuity Testing : For testing the continuity, probes TP1 and TP2 are used. If there is open circuit no LED lights. And if both the LEDs lights with equal intensity then continuity is ok.

The Semiconductor Tester is used to test diodes, transistors and also to test the continuity. Many times it is required to test the semiconducting components. This is a simple and inexpensive tester, used to test virtually any kind of semiconducting components such as switching diodes, transistors, power transistors etc. It is also useful in finding functional, short circuited and internally open devices in semiconductor batches.
About the Circuit :

• The circuit is build around IC1 which consists of four NAND gates. One of the gate from an RC oscillator. The oscillator signal is buffered and made available in true and inverted form by the three remaining gates.
• The two color LEDs (Red and Green) indicates the direction of the current flow or the device under test. Resistor R1 functions as a current limiter.
• The signals at the input and the output of IC1 are applied to a pair of test probes, a two-terminal test socket for diodes, and a three-terminal transistor. The base current for the transistor on test (TUT) can be set with preset P1.
• Only one LED lights when component is functional. When the component is internally open, no LED lights. The semiconductor with internal short circuit is easily recognized by the glowing of both the LEDs with equal intensity.

The testing procedure for diodes, transistors and continuity testing is as follows :

• Transistor Testing : Transistor to be tested must be connected with the base, emitter and collector pins to the indicated socket terminal. If Red LED glows then transistor is PNP type. And if green LED glows then it is NPN type. If transistor is not functional no LEDs glows and if it is short both LEDs glows with equal intensity.
• Diode Testing : With this tester we can test the cathode and anode terminals of a Diode. As above place DUT in the indicated socket. If Red LED glows then the terminal, which is connected to TP1 is cathode and other is anode. If Green LED glows then the terminal connected to TP1 is anode and other is cathode. Testing of functionality and short circuiting is same as described in transistor testing.
• Continuity Testing : For testing the continuity, probes TP1 and TP2 are used. If there is open circuit no LED lights. And if both the LEDs lights with equal intensity then continuity is ok.