RE: [Autopilot] MOSFETS vs power transistors

[Duncan M. <du...@fa...>]

Nope. Mosfets main claim to fame is easy interfacing since they are
voltage driven devices. Mosfets have other characterisitics that make
them better in efficiency like no minority carrier charge storage which
is why they are used in switch-mode power supplies. There is also
negative thermal coefficient and safe operating area, but not a problem
unless you are driving big motor loads. BJT's, being current drive are
typically more complicated to interface to for low drive interface
logic. But if you like the specs and can drive it, go for it. Since you
are talking open drain, you have to sink current so you have to use PNP
transistors to drive your load.

Duncan

> -----Original Message-----
> From: aut...@li... 
> [mailto:aut...@li...] On 
> Behalf Of Michael Shantz
> Sent: Monday, January 05, 2004 1:50 PM
> To: aut...@li...
> Subject: [Autopilot] MOSFETS vs power transistors
> 
> 
> I'm doing timer based PWM output from a microcontroller to 
> very small motors.  I notice that on-Resistance in the new 
> high gain transistors is as low or lower than for mosfets and 
> mosfets are annoying to work with so I'm thinking of using 
> power transistors.  The current, and power dissipation are 
> fine.  The open-drain I/O pin of the microcontroller can 
> handle the base
> current.   Plus transistors are cheaper.
> 
> Am I overlooking something?
> 
> Michael Shantz
> 
> 
> 
> 
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