Question on Bootstrapping

Thread Starter

jaydnul

Joined Apr 2, 2015
175
I've seen a lot of different definitions of bootstrapping, so what does it actually mean? I've seen the term used to describe a component or device used to pull up the voltage on a node for startup purposes. I've also seen it used to describe the technique of pulling up the operating point of a MOSFET. I've ALSO seen it used to describe the technique of using positive feedback to increase the input resistance of the feedback amplifier. So which is it, all of them?

Also, if you have a negative feedback amplifier, the input resistance is boosted by Rin(1+bA). So how does positive feedback increase the input resistance?

Thanks in advance!
 

shortbus

Joined Sep 30, 2009
10,045
You seem to be confusing "bootstrapping" with "feed back". The bootstrap I'm familiar with is the one having to do with "high side mosfets" it is charging up a capacitor to allow a Nmosfet to switch on when used in the 'high side'. Meaning a Nmos before a device that is controlled. It allows the gate of the mosfet to be at a higher voltage than the source of the Nmos, so it can be turned on.
 
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