IRF3250 and PWM

[taos]

Hi!
I need to calculate the optimal resistors to put in the gate,drain,etc... in my IRF3250.
I'm sending a PWM from a IC (0-5v) to make speed regulation from 0V-24V to a DC motor. I don't have a linear response, when my PWM goes from 0,3v-0,5V-0,9V I have 1v-11V-24V respectively in the IRF3250. have anyone a example or a resistor calculator to get a linear (0-24V) output from a 0v-5v input?
Thanks in advance!

 

[audioguru]

I couldn't find the datasheet for an IRF3250.
Most Mosfets need +10V on their gate to fully turn on.
PWM is full amplitude pulses and their pulse width is changed, not the voltage, to control the average output power by changing the duty-cycle of the pulses.
The Mosfet is used as an on-off switch in a PWM circuit. If it was linear then it would get very hot and waste a lot of power.

 

[Analog]

I couldn't find that part either.

 

[taos]

Sorry, I make a mistake, the part is IRF3205
datasheet https://www.electro-tech-online.com/custompdfs/2006/12/irf3205.pdf
for your answer, then what kind of component will be more reliable to have a linear output (0-24V) from a 0-5V input)?
Thanks in advanced

 

[Analog]

Looks like this device needs about 10V to fully turn on. As audio guru said, PWM is all about turning a device fully on or fully off. The output should look like a series of pulses (i.e. pulse width modulation). When you asked about a linear output, it really makes no sense with PWM. The motor may ultimately respond in a linear way, because it is acting like a low pass filter.

 

[taos]

Looks like this device needs about 10V to fully turn on. As audio guru said, PWM is all about turning a device fully on or fully off. The output should look like a series of pulses (i.e. pulse width modulation). When you asked about a linear output, it really makes no sense with PWM. The motor may ultimately respond in a linear way, because it is acting like a low pass filter.

With the PWM, I get in the pinout of my PIC a output that goes between 0V-5V.
The output of my pic always put 5V but changing the time that turning on/off (switching very fast) I can get values between 0-5V.This is the only matter to put analog values from my PIC and this is made by software.
With this output I need a component to translate this to 0V-24V. I have read something about using darlingtons or simple transistors but I have not found any example.
Thanks for your time

 

[audioguru]

You need a Mosfet Driver IC or make your own with transistors, to translate the 0V and +5V pulses from the PIC to 0V and +10V pulses needed for the gates of the Mosfets.

Your circuit operates with PWM. A linear circuit is completely different. A motor operates the same with either circuit.