Dynamic Amplifier

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Anonymous
Not applicable

 I want to use capsense slider and buttons to amplify a voltage waveform that I am getting externally.

   

I am not able to think what might be needed.

   

My problem statement is as follows: I need to take a waveform and depending on the slider position, amplify it. Everytime the capsense buttons are pressed, an offset is added to the voltage waveform.

   

For now, if I can display the amplified and offset adjusted waveform, it shall be enough

   

Any help will be highly appreciated.

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ETRO_SSN583
Level 9
Level 9
250 likes received 100 sign-ins 5 likes given

          There are several approaches to amplify –

1)    Use external transconductance OpAmp and IDAC in PSOC to control its G.

2)    Use A/D then multiply its values by desired G, and pass back to VDAC. This
Approach constrained to 8 bit precision by VDAC.

3)    2) but use PWM to create DAC, BW limited approach.

4)     Use PGA and control ist G setting. However it has limited G resolution, 9 G’s
between 1 and 50 available. Basically 3 bits resolution.

Regards, Dana.

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Anonymous
Not applicable

 I dont want to use method 2 since that will require unnecessary conversion from analog to digital and digital to analog

   

Is there a way I can use method 3 i.e. use a PGA but still get other gains of 1, 3, 5, 6 etc?

   

Please elaborate on method 1.

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HeLi_263931
Level 8
Level 8
100 solutions authored 50 solutions authored 25 solutions authored

The PGA comes only with fixed gain settings.

   

For transconductance amplifiers, see e.g. at TI. There you can also find variable gain amplifiers and multipliers, which might also help you.

   

Can you explain a little bit more why you need such a fine control over the amplification? I would have guessed that the gain settings of the PGA are enough for most cases...

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Anonymous
Not applicable

 That's right but my problem demands that as i move the capsense slider, the gain shd increase evenly... not in jumps..
Also, can you help me a little on adding an offset on button presses. I want that just as I press a capsense button, my input wave shifts either up or down depending whether the right or left button is pressed

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ETRO_SSN583
Level 9
Level 9
250 likes received 100 sign-ins 5 likes given

Here are some V controlled solutions -

   

 

   

    

   

          

   

http://www.ti.com/lit/ds/symlink/vca810.pdf

   

http://www.ti.com/lsds/ti/amplifiers-linear/variable-gain-amplifier-products.page

   

http://www.analog.com/static/imported-files/faqs/FAQ%20VGA%20FINAL%2005-08.pdf

   

http://www.ti.com/lsds/ti/amplifiers-linear/transconductance-amplifier-products.page?paramCriteria=n...

   

   

 

   

Using JFET to control G. Use depletion mode FETs for + control V.

   

    

   

          

   

 

   

http://www.next.gr/uploads/135-8976.png

   

http://i.stack.imgur.com/9WimI.png

   

 

   

Use multiplier -

   

 

   

    

   

   

          

   

http://www.analog.com/en/special-linear-functions/analog-multipliersdividers/ad633/products/product....

   

http://www.ti.com/paramsearch/docs/parametricsearch.tsp?family=analog&familyId=1472&uiTemplateId=NOD...

   

   

   

 

   

Regards, Dana.

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ETRO_SSN583
Level 9
Level 9
250 likes received 100 sign-ins 5 likes given

An example of a trasnconductance amp -

   

 

   

    

   

          http://www.onsemi.com/pub_link/Collateral/NE5517-D.PDF

   

 

   

Also investigate consumer audio parts, cheap, some have G control.

   

 

   

Regards, Dana.

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