help with producing a high rated current pulse

[mandrake2002]

hello everyone,
thanks in advance for taking the trouble to read and reply

i am struck with a circuit here . i am aiming to produce a triangular current waveform which has to be used in a different circuit . i've given the simplified version of the circuit

max current 10A , frequency 10 KHz

        _______2 ohm_____
        |               |
        |               |
        |               |          
        40V         Mosfet  
        |                |
        |________________|

i am currently using MOSFET IRFP 250N. my gate drive voltage is a 5 V variable supply given from my computer(Vgs)

i am getting a linear current (Id) output when gate supply in the range of 3.5 to 3.9 and then it is suddenly shooting up and after that i am again getting a linear variation . This results in the distortion of my current waveform and so i am not able to implement it in my other circuitry

could you please help me with this problem or is there any other way to produce such a pulse like using IGBT or any other power device . please help

 

[audioguru]

The amount of current out of a Mosfet is not linearily controlled by its gate voltage. An opamp could be used to provide plenty of gain so that negative feedback will make its response very linear.

 

[mandrake2002]

hello audioguru,
thanks for taking the trouble .

are you suggesting a transconductance amplifier ? if so would it be stable for the current ratings that i specified (0-10A) and would it respond to a fast changing pulse of frequency 10 KHz .
and is it possible to obtain a gain of nearly 2A/V

i would be very glad if you can point out a suitable op-amp or atleast specify a link where i would get some info

thanks a lot .

 

[audioguru]

Here is a linear amp with your Mosfet providing up to 30A to a load. Its voltage gain is 2 but is easily changed by changing one of the feedback resistors. It will faithfully reproduce a triangle wave or any other shape of wave up to about 15kHz.
EDIT: Voltage gain is 2, not 1.