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Resistor and Capacitor in Parallel

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mvs sarma

Well-Known Member

forumlicker007

New Member
I told you. It is difficult to explain using normal words. It's beyond the existence of language...
CAUTION: Don't make them parallel at any cost!!!.
It will raise a big question mark(?) against the laws of physics and electronics.
 

mark_3094

New Member
so the value of the resistance is still 100 Ohms in this case, and the value of the capacitor is still 270pF?
Putting them in parallel does not change their values?

The capacitor is there as a filter (as it would be without the resistor) and the resistor is there to protect the base of the transistor (as it would if the capacitor wasn't there)?

Basically the two components are not interacting with each other, but are performing their own separate functions?

I hope that made sense...
 

ericgibbs

Well-Known Member
Most Helpful Member
hi Mark,
Two images:

The cap increases the drive to the base at switch ON and the voltage stored in the cap, drives the base negative at switch OFF.

Improves the switching speed of the transistor at the pulse/edges

Look at the overshoot of the edges pos and neg when the cap is present.
 

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mark_3094

New Member
I see...
Thanks for the diagrams. What software do you use?

Why does the base need to be driven to negative? Is that so the on / off is 'cleaner'?
 

ericgibbs

Well-Known Member
Most Helpful Member
I see...
Thanks for the diagrams. What software do you use?

Why does the base need to be driven to negative? Is that so the on / off is 'cleaner'?
LTSpice.

By driving the base negative the 'carriers' in the base region are quickly removed so the transistor switches OFF faster,

Cleaner isnt the correct term, it increases the switching speed so the edges are faster.
 
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