MOSFET in Linear Region

Vijeendra Nadgir

Intellectual 265 points

Other Parts Discussed in Thread: CSD17570Q5B, PMP

Can you support us to choose MOSFET, please find below the critical parameters

MOSFET – Requirements

Signal MOSFET-N Channel
Application is in the active region / Implement in Linear region, so that MOSFET can work as a precision resistor
Maximum load Current – 500mA
Vds – 24V
Gate Source threshold voltage – 1.5V
Gate Input – PWM generated by uC
Product application
- With variation in frequency / pulse width, voltage at the drain should vary
- Expected load range is 1.5V to 8V

Please let us know, if you need any further information. Thanks

If this is not the right forum, then can you please redirect??

over 10 years ago

0 Brett Barr1 over 10 years ago

TI__Mastermind 18200 points

Vijeendra,

I have a few questions to clarify exactly what stresses are going to be put on the FET.

If I understand you correct, the max power the FET would have to handle is 500mW * 8V or ~4W.

When you say 24Vds, is that the max input voltage or have you already given yourself some buffer?

0 Vijeendra Nadgir over 10 years ago in reply to Brett Barr1

Intellectual 265 points

Yes Maximum power is 4W

Vds Maximumis 24V

0 Brett Barr1 over 10 years ago in reply to Vijeendra Nadgir

TI__Mastermind 18200 points

Vijeendra,

I would recommend trying a large die (low Rdson) 30V SON5x6 FET. 4W is a lot of power for a discrete FET to consume so you'll have to be careful with your layout. The more copper you can surround the FET with, and the more air you can blow on it, the better.

The recently released CSD17570Q5B, for instance, might be a good fit.

http://www.ti.com/lsds/ti/power-management/n-channel-mosfet-transistor-products.page?DCMP=pmp_mosfet&HQS=MOSFET#p267=30;30&p1480=SON5x6&p2749=0.69;4

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MOSFET in Linear Region