Electronics > Beginners
Capacitors don't work like I thought, please help me understand.
<< < (6/6)
David Cutcher CEG:
I don't want to prolong your agony, but what are you expecting to happen here?
Nor do I want to sound presumptuous. But Don't depend on simulation programs to learn electronics.
I suggest if you want to see the action of a Capacitor, set up the following circuit on a bread board. Then try different size caps.
OH, and for R1, should be 220k  \$\Omega\$.
David Cutcher CEG "certified evil genius"
gilligan:

--- Quote from: David Cutcher CEG on April 17, 2019, 01:48:16 am ---I don't want to prolong your agony, but what are you expecting to happen here?
Nor do I want to sound presumptuous. But Don't depend on simulation programs to learn electronics.
I suggest if you want to see the action of a Capacitor, set up the following circuit on a bread board. Then try different size caps.
OH, and for R1, should be 220k  \$\Omega\$.
David Cutcher CEG "certified evil genius"

--- End quote ---

Without a scope, this shows a lot of interesting data that would be much harder for me to witness.
David Cutcher CEG:
Glad that you found this useful.
The text is set up for the complete beginner, and I assume that beginners don't have access to scopes. But scopes become necessary as a tool to visualize what we can't see. In the text, I introduce scopes using a freeware program. I asked the community here for a recommendation for a real intro level scope.  Suggestions All over the map, but the winner was for the Owon vds 1022i. 
I have a class (for intro to electronics) starting on Udemy on July 1st. Get back to me if you are interested. Just reply to this post.  I need some beta testers.

David Cutcher "Certified Evil Genius"
MrAl:
Hi,

What it looks like is that the large capacitor leakage would keep the MOSFET turned on part way.  The feedback would cause some intermediate voltage level on the drain if there was a drain resistor.  With no drain resistor there will just be some level of current flow in the drain and that seems to be what you are seeing.

Keep in mind that the input resistance of the MOSFET is extremely high so it only takes a small amount of leakage current through the cap to keep the mosfet turned on somewhat.  The more the cap leaks, the more the mosfet it turned on.
Navigation
Message Index
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod