Author Topic: Art of Electronics Bad Idea question  (Read 359 times)

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Offline avector

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Art of Electronics Bad Idea question
« on: October 19, 2019, 07:22:43 pm »
I recently bought Art of Electronics 3rd Edition, which does not have the "Bad Circuits" from the 2nd Edition. In pursing the material and the website, I came across this "Bad Circuit" for a high side power switch using PMOS:

https://artofelectronics.net/bckt-high-side_power_switch/

I see that the PMOS is going to take a long time to turn off with only ~480uA to increase gate voltage, but I don't see anything fatally wrong with the circuit. Yet everywhere else on the internet I looked used a BJT NPN instead of an NMOS to drive the gate. I was wondering if someone could look up this circuit in the 2nd Edition or if anyone knew more (or saw something obvious I missed)?
 

Offline edavid

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Re: Art of Electronics Bad Idea question
« Reply #1 on: October 19, 2019, 07:38:48 pm »
The maximum VGS of the P MOSFET is likely to be exceeded.
 
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Offline Zero999

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Re: Art of Electronics Bad Idea question
« Reply #2 on: October 19, 2019, 08:58:34 pm »
Fortunately it's easy to fix by adding another resistor.


Another alternative is a BJT with an emitter resistor.
 


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