OPA1678: TINA simulation (cut off frequency and waveform)

Roy Chou1

Part Number: OPA1678

Tool/software:

Hi Team,

My customer give me the below circuit and would like to get the transient waveform and frequency response. I tried to use TINA to build the model. Can you help check it and modify if there is something wrong?

8030.OPA167x differential 02042025_1.TSC

In addition, how can I get the separate waveform for every in and out?

Regards
Roy

Regards.

Roy

7 months ago

0 Alex Curtis 7 months ago

TI__Intellectual 2710 points

Hi Roy,

I'd be happy to help. To start, could you provide some additional information about the circuit, such as the intended gain, cutoff frequency, and maximum amplitude of EXT_FR/EXT_FL? With the design goals I can verify that the circuit is working as you expect.

So far:

I've modified the input signals to be differential instead of single ended.
I noticed that the input signals range from -14V to 14V. Is this correct?

8030.OPA167x differential 02042025_new.TSC

Best Regards,

Alex Curtis

0 Roy Chou1 7 months ago in reply to Alex Curtis

TI__Genius 16210 points

Hi Alex,

Thank you. The file that you provided is what we expected. But may you help convert to AC analysis file? We want to check gain/phase for the circuit.

Regards,
Roy

0 Alex Curtis 7 months ago in reply to Roy Chou1

TI__Intellectual 2710 points

Hi Roy,

To run the AC analysis, there can only be one input voltage source, so I connected EXT_FR to both the left and right inputs. Below is the resulting closed loop response of the circuit (AUX_R and AUX_L).

8030.OPA167x differential AC.TSC

Please let me know if you have any questions.

Best Regards,

Alex Curtis

0 Roy Chou1 7 months ago in reply to Alex Curtis

TI__Genius 16210 points

Hi Alex,

I would like to use below circuit to do the AC analysis and get cut off frequency = 100kHz. May you help modify for us?

8030.OPA167x differential AC (1) (1).TSC

Regards,

Roy

0 Alex Curtis 7 months ago in reply to Roy Chou1

TI__Intellectual 2710 points

Hi Roy,

I can help modify this new circuit, but I would like more information on the other performance requirements of the filter, such as the passband gain and lower cutoff frequency. Currently the passband gain is -19.77dB (0.1 V/V) and the lower cutoff frequency is around 0.694 Hz. I want to clarify these requirements especially since this circuit has different component values than the one I sent previously, and the left channel was removed.

Best Regards,

Alex Curtis

0 Roy Chou1 7 months ago in reply to Alex Curtis

TI__Genius 16210 points

Hi Alex,

If customer would like to have +/-8V sine wave as Vin. Vout is 2.8V with +/-1V amplitude. May you help redesign the RC value for us?

We would like to have low pass filter with cut off frequency = 100kHz.

Regards,

Roy

0 Alex Curtis 7 months ago in reply to Roy Chou1

TI__Intellectual 2710 points

Hi Roy,

I modified the component values in the circuit you sent so that the cutoff frequency is 100kHz, then I adjusted the gain and common mode voltage so the output is +/-1V with a 2.8V offset.