Question relative to pads for capacitors - high frequency





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$begingroup$


In the article
Compact sub nano second pulse generator using avalanche transistors, I read P. 874




Further, we used pads on a doublesided
0.062” FR-4 epoxy glass laminate pc-board for
capacitors C6-C8 instead of soldering on 3 ATC capacitors.
Since the pc-board dielectric has a low series inductance,
this improves the pulse rise time significantly. Previous
attempts to use pc-board capacitances for low values of
capacitors [5] have used complex construction techniques
such as dielectric wedges to accommodate the avalanche
transistors and their bias networks with the pc-board
capacitors. However, our design simply lays out the
capacitors as pc-board traces (Figure 3) that easily connect
to the transistors.




I would like to understand what are these "pads" and how this improve the rise time significantly ?










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$endgroup$








  • 2




    $begingroup$
    the "pads" indicates "solder pads", the rectangular regions on a PCB where the surface-mount components are installed. The pads are connected with narrow "traces". Pads likely would be large rectangular regions of copper foil.
    $endgroup$
    – analogsystemsrf
    2 days ago


















4












$begingroup$


In the article
Compact sub nano second pulse generator using avalanche transistors, I read P. 874




Further, we used pads on a doublesided
0.062” FR-4 epoxy glass laminate pc-board for
capacitors C6-C8 instead of soldering on 3 ATC capacitors.
Since the pc-board dielectric has a low series inductance,
this improves the pulse rise time significantly. Previous
attempts to use pc-board capacitances for low values of
capacitors [5] have used complex construction techniques
such as dielectric wedges to accommodate the avalanche
transistors and their bias networks with the pc-board
capacitors. However, our design simply lays out the
capacitors as pc-board traces (Figure 3) that easily connect
to the transistors.




I would like to understand what are these "pads" and how this improve the rise time significantly ?










share|improve this question









$endgroup$








  • 2




    $begingroup$
    the "pads" indicates "solder pads", the rectangular regions on a PCB where the surface-mount components are installed. The pads are connected with narrow "traces". Pads likely would be large rectangular regions of copper foil.
    $endgroup$
    – analogsystemsrf
    2 days ago














4












4








4





$begingroup$


In the article
Compact sub nano second pulse generator using avalanche transistors, I read P. 874




Further, we used pads on a doublesided
0.062” FR-4 epoxy glass laminate pc-board for
capacitors C6-C8 instead of soldering on 3 ATC capacitors.
Since the pc-board dielectric has a low series inductance,
this improves the pulse rise time significantly. Previous
attempts to use pc-board capacitances for low values of
capacitors [5] have used complex construction techniques
such as dielectric wedges to accommodate the avalanche
transistors and their bias networks with the pc-board
capacitors. However, our design simply lays out the
capacitors as pc-board traces (Figure 3) that easily connect
to the transistors.




I would like to understand what are these "pads" and how this improve the rise time significantly ?










share|improve this question









$endgroup$




In the article
Compact sub nano second pulse generator using avalanche transistors, I read P. 874




Further, we used pads on a doublesided
0.062” FR-4 epoxy glass laminate pc-board for
capacitors C6-C8 instead of soldering on 3 ATC capacitors.
Since the pc-board dielectric has a low series inductance,
this improves the pulse rise time significantly. Previous
attempts to use pc-board capacitances for low values of
capacitors [5] have used complex construction techniques
such as dielectric wedges to accommodate the avalanche
transistors and their bias networks with the pc-board
capacitors. However, our design simply lays out the
capacitors as pc-board traces (Figure 3) that easily connect
to the transistors.




I would like to understand what are these "pads" and how this improve the rise time significantly ?







capacitor pulse high-frequency high-speed pad






share|improve this question













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asked 2 days ago









MikeTeXMikeTeX

640416




640416








  • 2




    $begingroup$
    the "pads" indicates "solder pads", the rectangular regions on a PCB where the surface-mount components are installed. The pads are connected with narrow "traces". Pads likely would be large rectangular regions of copper foil.
    $endgroup$
    – analogsystemsrf
    2 days ago














  • 2




    $begingroup$
    the "pads" indicates "solder pads", the rectangular regions on a PCB where the surface-mount components are installed. The pads are connected with narrow "traces". Pads likely would be large rectangular regions of copper foil.
    $endgroup$
    – analogsystemsrf
    2 days ago








2




2




$begingroup$
the "pads" indicates "solder pads", the rectangular regions on a PCB where the surface-mount components are installed. The pads are connected with narrow "traces". Pads likely would be large rectangular regions of copper foil.
$endgroup$
– analogsystemsrf
2 days ago




$begingroup$
the "pads" indicates "solder pads", the rectangular regions on a PCB where the surface-mount components are installed. The pads are connected with narrow "traces". Pads likely would be large rectangular regions of copper foil.
$endgroup$
– analogsystemsrf
2 days ago










2 Answers
2






active

oldest

votes


















6












$begingroup$

I hope you know that a capacitor basically consists of two electrically conductive plates which are close together but do not touch.



There can also be a dielectric (non conductive!) material in between. That could be FR-4 epoxy glass PCB material, like mentioned in the article.



enter image description here



We can then use the copper on the PCB to make the conductive plates.



They call that plate a "pad" which is a common name for a small (square) area on a PCB.



So those "pads" are just the plates of the capacitors they are making themselves.



This results in "better" capacitors than "normal" capacitors like:



enter image description here



In the situation described in the article, they only need very small value capacitors (the largest is 120 pF) so then PCB capacitors are an option, their size would not be very large.



Due to the nice dielectric properties of the FR-4 material, the PCB capacitors have even better performance than "normal" capacitors, like a lower ESR (Equivalent Series Resistance). That means less losses and better transient behavior.






share|improve this answer









$endgroup$





















    5












    $begingroup$

    A 'pad' on a board is simply an area of copper.



    In very high frequency work, it's often used for capacitors to ground, with values lower than 1pF. For any given dielectric and thickness, a certain area of pad will give you a certain capacitance. There are calculators available to estimate capacitance from geometry.



    The great advantage of such a capacitor to ground is that it does not have the fraction of nano-Henry lead inductance that packaged devices have.






    share|improve this answer









    $endgroup$














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      2 Answers
      2






      active

      oldest

      votes








      2 Answers
      2






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes









      6












      $begingroup$

      I hope you know that a capacitor basically consists of two electrically conductive plates which are close together but do not touch.



      There can also be a dielectric (non conductive!) material in between. That could be FR-4 epoxy glass PCB material, like mentioned in the article.



      enter image description here



      We can then use the copper on the PCB to make the conductive plates.



      They call that plate a "pad" which is a common name for a small (square) area on a PCB.



      So those "pads" are just the plates of the capacitors they are making themselves.



      This results in "better" capacitors than "normal" capacitors like:



      enter image description here



      In the situation described in the article, they only need very small value capacitors (the largest is 120 pF) so then PCB capacitors are an option, their size would not be very large.



      Due to the nice dielectric properties of the FR-4 material, the PCB capacitors have even better performance than "normal" capacitors, like a lower ESR (Equivalent Series Resistance). That means less losses and better transient behavior.






      share|improve this answer









      $endgroup$


















        6












        $begingroup$

        I hope you know that a capacitor basically consists of two electrically conductive plates which are close together but do not touch.



        There can also be a dielectric (non conductive!) material in between. That could be FR-4 epoxy glass PCB material, like mentioned in the article.



        enter image description here



        We can then use the copper on the PCB to make the conductive plates.



        They call that plate a "pad" which is a common name for a small (square) area on a PCB.



        So those "pads" are just the plates of the capacitors they are making themselves.



        This results in "better" capacitors than "normal" capacitors like:



        enter image description here



        In the situation described in the article, they only need very small value capacitors (the largest is 120 pF) so then PCB capacitors are an option, their size would not be very large.



        Due to the nice dielectric properties of the FR-4 material, the PCB capacitors have even better performance than "normal" capacitors, like a lower ESR (Equivalent Series Resistance). That means less losses and better transient behavior.






        share|improve this answer









        $endgroup$
















          6












          6








          6





          $begingroup$

          I hope you know that a capacitor basically consists of two electrically conductive plates which are close together but do not touch.



          There can also be a dielectric (non conductive!) material in between. That could be FR-4 epoxy glass PCB material, like mentioned in the article.



          enter image description here



          We can then use the copper on the PCB to make the conductive plates.



          They call that plate a "pad" which is a common name for a small (square) area on a PCB.



          So those "pads" are just the plates of the capacitors they are making themselves.



          This results in "better" capacitors than "normal" capacitors like:



          enter image description here



          In the situation described in the article, they only need very small value capacitors (the largest is 120 pF) so then PCB capacitors are an option, their size would not be very large.



          Due to the nice dielectric properties of the FR-4 material, the PCB capacitors have even better performance than "normal" capacitors, like a lower ESR (Equivalent Series Resistance). That means less losses and better transient behavior.






          share|improve this answer









          $endgroup$



          I hope you know that a capacitor basically consists of two electrically conductive plates which are close together but do not touch.



          There can also be a dielectric (non conductive!) material in between. That could be FR-4 epoxy glass PCB material, like mentioned in the article.



          enter image description here



          We can then use the copper on the PCB to make the conductive plates.



          They call that plate a "pad" which is a common name for a small (square) area on a PCB.



          So those "pads" are just the plates of the capacitors they are making themselves.



          This results in "better" capacitors than "normal" capacitors like:



          enter image description here



          In the situation described in the article, they only need very small value capacitors (the largest is 120 pF) so then PCB capacitors are an option, their size would not be very large.



          Due to the nice dielectric properties of the FR-4 material, the PCB capacitors have even better performance than "normal" capacitors, like a lower ESR (Equivalent Series Resistance). That means less losses and better transient behavior.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered 2 days ago









          BimpelrekkieBimpelrekkie

          51.4k246114




          51.4k246114

























              5












              $begingroup$

              A 'pad' on a board is simply an area of copper.



              In very high frequency work, it's often used for capacitors to ground, with values lower than 1pF. For any given dielectric and thickness, a certain area of pad will give you a certain capacitance. There are calculators available to estimate capacitance from geometry.



              The great advantage of such a capacitor to ground is that it does not have the fraction of nano-Henry lead inductance that packaged devices have.






              share|improve this answer









              $endgroup$


















                5












                $begingroup$

                A 'pad' on a board is simply an area of copper.



                In very high frequency work, it's often used for capacitors to ground, with values lower than 1pF. For any given dielectric and thickness, a certain area of pad will give you a certain capacitance. There are calculators available to estimate capacitance from geometry.



                The great advantage of such a capacitor to ground is that it does not have the fraction of nano-Henry lead inductance that packaged devices have.






                share|improve this answer









                $endgroup$
















                  5












                  5








                  5





                  $begingroup$

                  A 'pad' on a board is simply an area of copper.



                  In very high frequency work, it's often used for capacitors to ground, with values lower than 1pF. For any given dielectric and thickness, a certain area of pad will give you a certain capacitance. There are calculators available to estimate capacitance from geometry.



                  The great advantage of such a capacitor to ground is that it does not have the fraction of nano-Henry lead inductance that packaged devices have.






                  share|improve this answer









                  $endgroup$



                  A 'pad' on a board is simply an area of copper.



                  In very high frequency work, it's often used for capacitors to ground, with values lower than 1pF. For any given dielectric and thickness, a certain area of pad will give you a certain capacitance. There are calculators available to estimate capacitance from geometry.



                  The great advantage of such a capacitor to ground is that it does not have the fraction of nano-Henry lead inductance that packaged devices have.







                  share|improve this answer












                  share|improve this answer



                  share|improve this answer










                  answered 2 days ago









                  Neil_UKNeil_UK

                  78.7k285182




                  78.7k285182






























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