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MOSFET Needed

I am looking for an inexpensive P-Channel enhancement node SOT-23 case MOSFET that will suit my design. See

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The M9 transistor will have a source voltage of between 18 and 28 volts maximum. Getting a MOSFET whose Source - Drain voltage (when off, in this case) is greater than 28 volts is no issue. I can easily get them for under $0.10. Getting one capable of handling a measly 1/2 milliamp or so is also no big deal. The problem I am having is finding one rated for more than 20 volts Soource - Gate voltage, which will be the case when the gate of M7 is high, turning the circuit on. At this point the source voltage of M9 may be as high as 28 volts, and the gate voltage will be near zero. I am doing it this way, because the source voltage of M9 is the power input voltage of the circuit, and I need the drain voltage of M9 to be as close to the power input as possible, so I can accurately measure it at the junction of R6 and R11 using an ADC.

Reply to
rhor...
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There are a few, e.g. DMP3056L.

As Jan said, an extra resistor would help, and your impedance levels are on the high side, if you want the FET to turn off rapidly.

Cheers

Phil Hobbs

Reply to
Phil Hobbs

Add a resistor, as Jan says, if you want to stay within the abs-max of the pfet. In real life, most pfets would survive 28 g-s; they usually die around 60 or so.

You can also buy protected-gate mosfets, which actually have a s-g zener, usually around 40 volts, but spec survival when the gate is over-driven.

Reply to
John Larkin

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