This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Tina simulate issue.

Other Parts Discussed in Thread: OPA1611, OPA1602

Here's a simple schmatics and the simulation result. The signal generator setting is : 1M Hz, sine wave, 1V rms. The green wave is VF1, the brown wave is VF2. I think VF2 should be VF1*1K/(1K+470), so the should have same form , just have different level. but the simulate result shows that VF2 is much more different, I wonder know why.

  • Eric,

    Thank you for looing into the use of the OPA1611. The OPA1611 is not well suited for such a high capacitive load. Please refer to figures 19 and 20 in the OPA1611 data sheet (SBOS450C). It appears as if you are trying to place a 159KHz low pass filter in the signal path. What is the purpose of this filter and what is the purpose of this amplifier.

  • Thank you for you reply. I was looking for the reason of self-excitation of audio amplifer. the acture OP I am using is OPA1602, which I can't find in the lib, so I replace it with OPA1611 and simulate. I use 1M Hz sine wave connect to first op's plus input as noise source, and see this curious wave form, I thought it's may be the reason of self-excitation, then I post this question. Anyway, it truns out that self-exciation was caused by parasitic cap(use 1nF as substitute in schmetics, and it's much smaller in acture.), and I solve the problem by replace the 1K resistor between first op's output and sencond op's input with  a 0 Ohm resistor.