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TL074: Possibility of oscillation due to failure

Satoshi
Guru 19635 points
Part Number: TL074
Other Parts Discussed in Thread: TL081H

Tool/software:

A problem occurred where several TL074IDRs oscillated.

I'm investigating whether EOS is the cause, or if there is a problem with the circuit and the oscillation is caused by variations in IC characteristics.

- If there are any parts of the attached circuit diagram that can be improved, would you please let me know?

- I am currently thinking of the following improvement plan. Is it correct?

  1. Add a capacitor to the output stage (8Pin)

  2. Check the power supply sequence of VCC+ and VCC- (Prevent VCC- from power up first)

- If there is no particular amendment proposal, is it likely that it is due to EOS?

[Supplementary information]

- The waveform during oscillation is attached.

   ch1: 3OUT (8Pin), ch2: VCC- (-15V), ch3: VCC+ (15V)

- 1IN+ (3Pin) and 2IN+ (5Pin) are connected to GND.

- Confirmed that the problem was resolved by replacing with a normal part.

- 1OUT (1Pin) and 2OUT (7Pin) have no oscillation.

- C1 and C2 are connected close to the power supply pins.

Best regards,

Satoshi

  • 0
    TI__Guru 72681 points

    Hi Satoshi-san,

    Can you share the schematic with us? Without the schematic, it is difficult to gauge what is going on. It is likely that the circuit does not have adequate phase margin and result the Vout to oscillate. 

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    Guru 19635 points

    Hi Raymond-san

    Thank you for reply,

    I have attached the circuit diagram again.

    (All capacitors are 0.1μF and resistors are 20kΩ.)

    These four OPAMPs are TL074 ch1 to ch4 and the inputs are also connected to GND, so there are no other circuits before or after them.

    It has been independently evaluated in TL074.

    Best regards,

    Satoshi

  • +1 in reply to Satoshi
    TI__Guru 72681 points

    Hi Satoshi-san,

    Ok, I see that you may have issues. Please configuration your test circuit as shown below exactly. Please let me know if the issue persists. 

    TL074H Oscillation issies 02262025.TSC

    The 100kohm at the input is to address the bias current return to GND issue. I do not know how you set it up, though you did mention that the input is tied to GND. If that is the base, you do not have output signal and it should not oscillate. 

    At the output, I place 100ohm resistor at the output. If the output is driving capacitive load, such as scope probe with 15pF or higher parasitic capacitance, you may have seen oscillation issue (if the TL081H does not have adequate phase margin in the circuit). 

    Please let me know if test results and I will resolve the issues once I understand your setup. 

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    TI__Guru 72681 points

    Hi Satoshi-san,

    I am going to close this query, since I have not heard from you. 

    If you have other questions, please let us know. 

    Best,

    Raymond 

    HVA Application Team

  • 0 in reply to Raymond Zhang1
    Guru 19635 points

    Hi Raymond,

    Sorry for my reply delay, and thank you very much for your kind answer.

    I'll check the "resolved" soon.

    Best regards,

    Satoshi