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Other Parts Discussed in Thread: LM6154

The Filter design tool:

It is not possible to lock a amplifier. 

It takes a lot of time to set it back each time.

Bug: It is not possible to lock E24 resitor and capicitors. When a export is done or print then the tool resets to default. ideal values are prited only.

  • Morning Paul, 

    Picking an amplifier (nor best fit standard RC solutions) have been a priority in the TI tools. Unlikely those will be upgraded soon, But - if you had some specific requirements , detail those out and perhaps I can do something, 

    I spent some time trying to benchmark tools in these articles, that is some time ago now, but things don't move fast in this area,

  • Paul,

    Thank you for reaching out to us!

    Could you please clarify your statement of the tool is not possible to lock an amplifier?

    Do you mean there is no amplifier recommended by the tool, or when you select an alternate amplifier, the new amplifier does not replace the old amplifier?

    If formal, could you please provide the specification? For example, what is the filter type? What is the filter response, cutoff freq, stopband freq and etc?

    In order to lock the E24 for resistor and capacitor, please click on the UPDATE DESIGN button after selecting E24 for resistor and capacitor.



  • Dear Alfred,

    I want to design a low pass filter and a high pass filter:

    50kHz with ripple 0,3dB

    And as fast down as possible to -100dB

    For the High pass: (at the -100dB) stopband 17kHz is probably the best I can get for the sharpest result at -100dB stopband.

    This 17kHz is found manually with typing each time a different value and looking at the tool to keep the 4 stages maximum.

    4 stages

    Sallen key circuit

    E24 resistor 1%

    E24 capacitor 5%

    Amplifier: LM6154

    For the low pass filter and the high pas filter:

    I want with the same parameters to design 7 other lowpass and 7 other high pass filters. With a other freqency bud the same amplifier. (And of coarse other capacitors and resistors.)

    The E24 resistor and capacitor change:

    I have used the update button. But the report it produced is without the E24 resistor and capacitor. (Ideal is used , not even E96!)

    If I want to use the LM6155 amplifier, I select it myself.

    Bud with other changes, like stopband freq adjustment, or E24 resistor adjustment. The tool changes the amplifier itself.

    I want the tool to keep the amplifier and the resistor E24 and capacitor E24 the same.

    (Resistor E24 and capacitor goes back to E96 each time I change something else. Just like the amplifier will be changed bij the tool itself to a other.)

    Met vriendelijke groet,

    Paul van Dam

  • Morning Paul, 

    Lot of detail there, taking the low pass piece of this - 

    50kHz with 0.3dB ripple - ok, 


    "And as fast down as possible to -100dB" is not a design spec as you need to consider complexity tradeoffs. Usually, folks go Chebychev for fast rolloff but again you need a target like -100dB at 100kHz or something like that - the closer to ideal you ask, the more stages and less realizable it becomes. 

    Then, to select solutions, you also need to specify output swings and total gain - not enough to go on yet here. 

    For multiple stages with gain, the solutions are better using an ascending Q descending gain strategy. If the gain is 1 overall, ascending Q as in academia will be better. 

  • Paul,

    Thank you for your clarification!

    I see your challenge in locking a selected amplifier and E24 passive components when you need to go back to the specification page to refine your design.

    Currently, once a design is created and if you step back to specification page to change the design specification,

    the tool will create a new design and set the default passive components to E96 and pick a new amplifier that meets your new specification.

    The reason behind this is to save the design you have created so that you can retrieve it if needed.

    I really appreciate your feedback and show us how the tool can better make the design process more user friendly. I will add this feature to our backlog

    for future enhancement. For the report, Ideal is always used for the partnumber. The grade of the selected passive component is listed by the Tolerance

    under the property. For example, E24 would have a tolerance of 5%.