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testing components LM358A, LM339

Vaidehi Oruganti
Prodigy 10 points
Other Parts Discussed in Thread: LM339, LM358A

Hello,

I have an induction heater circuit with operational amplifiers LM358A and LM339.

The induction heater circuit consists a bridge rectifier, IGBT, PWM controller + MOSFET module, LC tank circuit, transformer and two operational amplifiers (mentioned above).The circuit as a whole has stopped functioning. The electrical connectivity is good and there are no faulty capacitors/traces. The diodes, rectifier, IGBT, transistors, transformer, inductors are still functional.

I am looking for a testing procedure for the two op-amps in my circuit. I have a function generator, oscilloscope, Digital multimeter, probes, LC meter, spare caps, DC supply, AC supply available for troubleshooting.

Please give me as many details as possible . I am a chemical engineering graduate student with little knowledge on troubleshooting electronics, but I'll be happy to learn.

Thank you,

Vaidehi

  • 0
    TI__Guru*** 140136 points
    Vaidehi,

    Do you plan to test the devices in the circuit or removed from the board?

    In circuit, verify power for VCC and GND pins. For LM339 measure voltage at each input pair to see if output should be high (with pull up) or low.
    For LM358A, check the output voltage is between supply rails. Both inputs should be the same voltage, but the circuit may not like a digital meter on input pins, so use a low capacitance oscilloscope probe