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LM833: Oscillation question about inverting op-amp circuit(about LM833DGK).

BOSEUNG KIM
Prodigy 40 points
Part Number: LM833
Other Parts Discussed in Thread: OPA1602,

Oscillation question about inverting op-amp circuit(about LM833DGK).

The circuit is configured as shown in Appendix 1, with a oscillation of 0.54v for input(A) and 1.19v for output(B) (The oscillation has 400kHz~800kHz frequency, Different board has different oscillation level )

No connection except for the following circuit and connecting a decoupling capacitor to power.

Oscillation was disappered when the "OPA1602" was connected.

When I using a single layer PCB connection then the oscillation occured, but using multi layers PCB then the oscillation disappeared.

I don't know the exact cause, but I think it's the conditions of the oscillation are satisfied on the multi layer PCB.

Question

1. Can the oscillation occur during configuration as shown in the circuit below?

2. The oscillation disppered when I conneting the C102(the value : 0.3pF). I don't think this was caused by a low-pass filter because the cut-off frequecy value is more than 1.5GHz

   I think connecting the capacitor has caused the oscillation to disappear because it has changed the conditions of the oscillation

  so, If the 10pF capacitor value is connected the C102 and the oscillation disappears, ask if it can be seen stable circuit.

     

  • 0
    TI__Guru 54041 points

    Hi ,

    Question

    1. Can the oscillation occur during configuration as shown in the circuit below?

    Yes, LM833 as configured below will oscillate, since there is a Q at approx. 840kHz. 

    Question:

    2. The oscillation disappeared when I connecting the C102(the value : 0.3pF). I don't think this was caused by a low-pass filter because the cut-off frequency value is more than 1.5GHz. I think connecting the capacitor has caused the oscillation to disappear because it has changed the conditions of the oscillation. so, If the 10pF capacitor value is connected the C102 and the oscillation disappears, ask if it can be seen stable circuit.

    When you inserted 0.3pF at C102, it still has a Q at approx. 800kHz, but the peaking in reduced somewhat. In order to de_Que the circuit, you need to insert approx. 1-2pF capacitor, where C = 1/(2*pi*800kHz*100kOhm)=2pF. 10pF may work as well, but your BW of the circuit is limited, but it will be stable. 

    Enclosed is the Tina Simulation: 

    /cfs-file/__key/communityserver-discussions-components-files/6/LM833-04272020.TSC

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    Prodigy 40 points

    Hi. Raymond

    Thank you for your Answer. It was very helpful.

    Boseung.