> > > You don't really have to design a FF, you can just get one from
> > > TI for example
> > > (www.ti.com/sc). Keep in mind, if you are using any rails in your
> > > circuit >5V,
> > > you will need to stick a NPN transistor on the output of your FF
> > > to switch on
> > > the P-channel mosfet. If you are just using +5 lines, then you are ok.
> >
> >         Huh? Why? A PMOS transistor used as a high side switch
> needs Vdd-Vth
> > to
>
> If you are using the PMOS on the high side of a +12line, Vdd -
> Vth (Assuming
> Vth is approx. 4-5V) = 7V, which isn't enough. For example, my IRF9530,
> connected to a +12V line, will turn on when the gate is grounded,
> and will turn
> off when it reaches +9V. One way to get +9V is by using an NPN
> connected to the
> FF. Like I said, if he is only using +5V, then it's not a
> problem...am I wrong
> here?

        Ah, THAT'S what you were talking about, the transistor not turning off. In
that case you are correct, however in a battery powered app (Josh mentioned
a Sony NiMH battery) voltages don't get anywhere near that high. TTYL

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