I have been looking up bootstrapping circuits. The concept makes sense, but I am afraid I just don't see the use. Can someone give a practical situation where one would be designing and decide this is a better option than anything else? The general case seems to be a high side FET gate drive.

  • 4
    \$\begingroup\$ bootstrapping what? Input impedance? A compiler? \$\endgroup\$ Jan 12, 2016 at 18:44
  • \$\begingroup\$ Are you doing this to get more voltage swing out of an audio output stage? \$\endgroup\$
    – Autistic
    Jan 12, 2016 at 18:48
  • \$\begingroup\$ I mean this in the sense of a bootstrap capacitor or when tying the output to the input. I am just not familiar with the practice of doing this. \$\endgroup\$
    – mcmiln
    Jan 12, 2016 at 18:49
  • \$\begingroup\$ For providing high side get drive to a FET for example? \$\endgroup\$
    – John D
    Jan 12, 2016 at 19:01
  • \$\begingroup\$ I believe that is what I am looking for. I have seen people use bootstrapping to drive an N-FET since the gate must be higher. It just doesn't stand out to me why this is the best option. \$\endgroup\$
    – mcmiln
    Jan 12, 2016 at 19:21

1 Answer 1


It is an easy method of allowing N-channel high-side drive where 100% (or near that) duty cycles are not required. You don't need extra circuitry for a charge pump. For example, if your high side FET is on a 100V rail, you're looking at generating a 110V "charge pumped" voltage from some other supply. Or you can use a bootstrap based circuit to "add" the 10V using a capacitor and a suitably rated driver circuit.

It is not necessarily "the best option" as you put it. For example, for applications requiring 100% duty cycle, you can't use this method (since the bootstrap capacitor is charged during the PWM off time). It happens to be an easy, readily used option that you can use for switching circuits.


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