Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

Gate capacitance and gate charge
Gate capacitance and gate charge
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 22nd January 2007, 02:27 PM   #1
rtarbell is offline rtarbell  United States
diyAudio Member
 
Join Date: Sep 2005
Default Gate capacitance and gate charge

For a large switching FET, in order to get the FET to switch quickly and to avoid excess power consumption, a large Vgs (usually >10V) must be supplied, along with a fair amount of current behind that Vgs supply (~1 amp of transient current for a large FET).

What is the difference between gate capacitance and gate charge, in terms of how much gate current/gate-source voltage needs to be applied? I thought the measure to be concerned about when switching a FET was gate charge, but how does gate capacitance come in to play?
  Reply With Quote
Old 22nd January 2007, 06:11 PM   #2
cliffforrest is offline cliffforrest  United Kingdom
diyAudio Member
 
Join Date: Sep 2004
Location: South Coast, UK
Gate capacitance and gate charge
The two are related.

It is Gate voltage which controls the D/S channel conductivity, but to get the gate to required voltage requires charging up the gate capacitance.

A useful formula is q = CV = IT (q = charge)

So if there is a high gate C, (large geometry) either Time is required (slow) or a large Current to charge it.

Think about the CV=IT bit.

It is very useful in understanding the relationships between C, V, I, T. linked by the concept of charge.
  Reply With Quote

Reply


Gate capacitance and gate chargeHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Gate drivers Jabbaz Class D 12 8th January 2005 03:03 AM
not gate oscilator sss Digital Source 6 24th October 2003 09:03 PM
best way to generate Gate-Drain or Gate-Source short in electret capsule JFET? capslock Parts 2 27th September 2002 09:07 AM
mosfet gate charge Diogo Solid State 12 19th August 2002 01:24 PM


New To Site? Need Help?

All times are GMT. The time now is 07:46 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki