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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Mattski wrote ...
... Thinking back a bit more I think part of the past problem is the battery trick was making it so that the FET did not turn entirely off, since when the 555 was outputting 0V there was still 3V going to the gate...
Yes, i thought that may be an issue if he elevated the gate to much, but below 4 volts it shouldnt have made that much of a difference i think.
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
Patrick wrote ...
Mattski wrote ...
... Thinking back a bit more I think part of the past problem is the battery trick was making it so that the FET did not turn entirely off, since when the 555 was outputting 0V there was still 3V going to the gate...
Yes, i thought that may be an issue if he elevated the gate to much, but below 4 volts it shouldnt have made that much of a difference i think.
There will be some current, not much but it will be through a voltage drop. Also when the diode in the buck converter is conducting the source of the FET will be held below circuit ground by the diode voltage drop, which further turns the FET back on.
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
haxor5354 wrote ...
im gonna order some p channel fets to make another buck converter is it okay if they still have the drain-source diode?
Yes, the drain-source "body" diode is fine in a buck converter as it should never be forward biased in a buck converter since it points from source to drain. Sometimes in other converters it matters, but mostly because as far as diodes go the body diodes are usually pretty slow, so you would externally add a faster diode if it mattered.
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help needed for a buck converter
