definition of "bootstrap" 2

[geomit]

Hello all,
I would really, really like to know what the definition of "bootstrap" is when applied to a function of some electronics.

Thank you

 

[Skogsgurra]

I assume that you know that a bootstrap is the strap on the back of boots. The straps were used to pull on the boots.

I also assume that you know about baron von Münchausen. He is said to be able to lift himself by pulling hard in his bootstraps.

So "to bootstrap" actually means that you do something seemingly impossible using only the resources available to you.

A couple of examples:

To boot a computer originally meant that you enterered a short machine code routine using the front panel switches (there were address switches and data switches and an enter button) this "boot strap routine" was then used to read the OS from a deck of cards or from a TTY tape. It is nowadays used in its short form "to boot", which means to restart a computer. The bios and OS are then read from ROM and from the hard disk. Those devices were not available to early computers so the code had to be entered manually. Things are a lot easier today.

The other example is from frequency inverters. There you need a gate control voltage that is a bit higher than the available DC link voltage to efficiently switch the high side transistors on. A boot strap circuit that uses a charge pump and the switching frequency of the inverter produces the needed voltage.

There are several other uses unknown to me.

I have sometimes heard the misconception that "to boot" means kicking something with your boot to make it start. That is not the case.

 

[jraef]

That (kicking) is how I used it when referring to my old PC! But come to think of it, it was doing something seemingly impossible with the limited resources...

 

[sreid]

This may not be the best definition but in an amplifier a bootstrap means to have a positive feedback internal to the amplifier to improve some parameter. One example is a bootstrap capacitor from the output of an audio amplifier to the top side driver stage to provide power to the driver stage input. Also, sometimes feedback from an amplifier, say, second stage, is fedback to the amplifier input stage to improve input impedance.