I need to create a test setup to do a long-term overvoltage test on a device. The specifications that need to comply with are given below:

[![Test Specifications](https://i.stack.imgur.com/AM8Pa.png)](https://i.stack.imgur.com/AM8Pa.png)

As you can see, I need a rise and fall time below three microseconds, and I don't have a power supply that can do that. I tried to do that by using two separate power sources. The first will have 36 V, and the second will have 24V. To switch between the two power supplies in under 3 microseconds, I planned to use NMOS. I made the circuit below as a reference. As the ID current will not exceed 150mA, I chose 1N4148 as a diode for reverse polarity, but I paralleled three of them to be safe. To give VGS= 0V/5V to the MOSFETs I used an Arduino UNO.

[![LtSpice circuit that I created](https://i.stack.imgur.com/z8RV0.png)](https://i.stack.imgur.com/z8RV0.png)

After examining the circuit, I observed the current at R2, as the figure below illustrates.

[![Current graph at R2 when the Vdd2 is 36V](https://i.stack.imgur.com/lw4JX.png)](https://i.stack.imgur.com/lw4JX.png)

After creating this circuit in a real lab and trying it, I observed a huge voltage drop. I can't read 36V at the Vout where I will put the device which will undergo the test when the 60 min test time comes. But according to LtSpice simulation, there shouldn't be a problem, as the figure below shows.

[![Vout graph](https://i.stack.imgur.com/3VOFn.png)](https://i.stack.imgur.com/3VOFn.png)

I increased Vdd2 until I read 36V at the Vout and set Vdd2 to 60V, but when I do that, the resistor 2(R2) starts to overheat (approximately 170C,) and it will absolutely burn when I start the 60 minute test in the future. I checked the current at the R2, and I read 40mA to 4mA at the multimeter. The 1k ohm resistor I used has a 5W limit, so it should withstand. What did I do wrong? Can you help me?

Here the datasheet for the [IRF540.](https://www.vishay.com/docs/91021/irf540.pdf)