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Transistor Tester Instructions

Here is the circuit of a very simple transistor tester that uses two LEDs to show the state of a transistor. Both PNP as well as NPN transistors can be tested using this circuit. Both the PNP as well as the NPN transistors can be tested with this circuit. Quad 2 input CMOS NAND gate IC CD4011B is the heart of the circuit. Quad 2 NAND the entrance door CMOS IC CD4011B is the heart of the circuit. Out of the four NAND gates inside the IC, only three are used here and they are used as NOT gates by shorting their input terminals. Of the four NAND gates inside the IC, only three are used here and are used as NO gates by a short circuit at their input terminals. Gates U1a, U1b, resistor R1 and capacitor C1 forms a square wave oscillator. Gates U1a, U1b, resistor R1 and capacitor C1 form a square-wave oscillator. The frequency of this oscillator can be adjusted by using R1.

The frequency of this oscillator can be adjusted by using R1. The output of the oscillator is inverted using the gate U1c. The output of the oscillator is inverted with the gate U1c. The inverted oscillator output is connected to the base of the transistor under test through the resistor R2 and the non inverted oscillator output is connected to the emitter of the transistor under test using the resistor R3. The output of the inverted oscillator is connected to the base of the transistor under test through resistor R2 and the non-inverted output oscillator is connected to the emitter of the transistor under test with resistor R3.

The status of the LEDs D1 and D2 reveals the condition of the transistor under test. The status of LEDs D1 and D2 reveals the condition of the transistor under test. If red LED is ON, it indicates that the transistor under test is a good NPN. If the red LED is lit, it indicates that the transistor under test is a good NPN. If green LED is ON, it indicates that the transistor under test is a good PNP. If the green LED is lit, it indicates that the transistor under test is a good PNP. If both LEDs are ON, it indicates that the transistor under test is short. If both LEDs are lit, this indicates that the transistor under test is short. If both LEDs are OFF, it indicates that either the transistor is bad or you may have connected it incorrectly. If both LEDs are off, it indicates that the transistor is bad or it is possible that you have connected it incorrectly.

LED Based Transistor Tester Kit


LED Based transistor tester kit

Circuit diagram. Circuit diagram
  • The circuit can be easily assembled on a Vero board. The circuit can be easily mounted on a Vero board.
  • Use 5V DC for powering the circuit. Use 5V DC to power the circuit.
  • All unused pins of the IC must be connected to ground. All pins not used in the IC must be grounded.

transistor tester circuit


transistor tester circuit


Here is a very simple circuit that can be used to check the hfe of the transistors. Both PNP and NPN transistors can be checked using this circuit. Both PNP and NPN transistors can be checked with this circuit. Hfe as high as 1000 can be measured by using this circuit.The circuit is based on two constant current sources build around transistors Q1 and Q2.The Q1 is a PNP transistor and the constant current flows in the emitter lead. As high as 1000 HF can be measured by using this circuit.The circuit is based on two constant current sources to build around the transistors Q1 and Q2.The Q1 is a PNP transistor and the constant current flows in the terminal of issuer. The value of constant current can be given by the equation; (V D1 -0.6) / (R2 + R4). The POT R4 can be adjusted to get a constant current of 10uA. The constant current value can be given by the equation; (V D1 -0.6) / (R2 + R4) The R4 POT can be adjusted to obtain a constant current of 10uA.

The Q2 is an NPN transistor and the constant current flows into the collector lead. The Q2 is an NPN transistor and the constant current flows in the main collector. The value of this constant current can be given by the equation; (VD2-0.6) / (R3 + R5) .The POT R5 can be adjusted to get a constant current of 10uA.This constant current provided by the Q1 circuit if the transistor under test is an NPN transistor and by Q2 circuit if the transistor under test is a PNP transistor is fed to the base of transistor under test. The value of this constant current can be given by the equation; (VD2-0.6) / (R3 + R5) The R5 POT can be adjusted to obtain a constant current of 10uA.This constant current provided by the circuit if transistor Q1.

Under test is an NPN and Q2 transistor by the circuit if the transistor under test is a PNP transistor is powered to the base of the transistor under test. This current multiplied by the hfe flows in the collector of the transistor and it will be indicated by the meter. This current multiplied by the HFE flows in the collector of the transistor and that will be indicated by the meter. The meter can be directly calibrated to read the hfe of the transistor. The meter can be calibrated to read directly the hfe of the transistor.









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Just ordinary people trying to get better

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