Webench/OPA2141: Webench Designer error

Hi,

I deliberately left Negative Supply (Vee) box empty (clear it), as I wanted use Single Supply voltage in this op-amp.

Should I always fill Vee even if I need Single Supply design?

Hi,
than this need be specified in that page, that Vee box must not be empty.

Should the "User Vref Choice" always set to "Recommended Vref " value that is automatically chosen by Webench?

Agreed. I'll inform the developers.

The automatically selected Vref value is the midpoint of the supply rails in order to give the best headroom.

If you must, after the design has been created, you can select the Vref symbol in the schematic and modify the value.

Thanks,
JC

JC Zhu - WEBENCH Design Center said:

The automatically selected Vref value is the midpoint of the supply rails in order to give the best headroom.

Example: I created Inverting op-amp design, Power Supply is 12V Single supply, and Webench offer the Vref voltage 2.15V which definitely is not 1/2 of the supply rails.

About Desired Input and Output Requirements - Vin Min, Vin Max - for audio signal input, Vin Min: should I specify negative value for minimal signal? The input signal is signal from audio line out.

There is no Help pages for Webench Amplifier Designer - where I can find it?

Wilson,

We are not sure what voltages that you require at the input and output of the inverting circuit. If you can specify these parameters it will be a little easier to solve your problem. Please send your numbers in your next reply.

In terms of the value of zero showing up in the Vee position, if you click on the 'Single Supply' button on the top you will see the a zero is programmed into the Vee position as a default. I think that our error in the programming is to not allow you to leave the Vee field blank.

Concerning your comments about the access to HELP for this tool, I am personally in the process of writing those documents and they will be available some time in Feburary, after the team has approved the final copy. But during the time between when we post the HELPS and now, please refer to the attached document. It will help you get through the  Amplifier Designer Requirements page.

INV_NINV__details_ Select .docx

Thank you for the Help doc. 

About the input / output voltage, in this case it can be Unity-Gain Inverting Amplifier 0dB (1V/V), the input voltage is line-out signal voltage, the AC signal, which I guess varies from the peak amplitude approx. +2.0 Vpk to the equivalent negative voltage (−2.0 Vpk).

Also, when I select parameters use "Input Voltage Range, Gain", Webench show "Error: Vin is beyond power supply voltage" .

Wilson,

Thank you for provided your input conditions. As I read your inputs

Vinpk-pk = 4

Vin Midpoint = 0

Closed loop gain = -1

User Vref Choise = 0

With these conditions the input swing is from -2 V to 2 V because of your Vin Midpoint selection,and a gain of -1  and Vref of 0, the output swing will be +2 V to -2 V. As you can see, the output swing of -2 V goes beyond and is less than the negative power supply of 0 V. This is why you are getting the error message. To correct this error Vref should be 1.25 V to 4.5 V.

Unfortunately, I am also noticing that the error message does not disappear when you do plug in ligitimate numbers. I will send a notice to the development team today to try to correct this problem . Meanwhile,  I sugggest you restart tjhe program. and use the single supply option and try to porgram using the first option.

Hi JC,

I have a question about using Webench,

  For example, I need to add more output capacitors in the design,

After I modified schematics, however I can only simulate startup state and can't simulate steady state.

Do you have a solution for it?

Thanks,

Hi JC,

   Thanks,

   Tony

Wilson,

This error has been corrected in code so no restart is required.