Hello,
I have built a circuit to give me a high voltage (0-150 V) pulse with adjustable pulse width (2-20 micro s) by discharging a capacitor via a MOSFET whose gate is controlled by a 5V signal with required pulse width. The circuit schematic is attached.
When I attach a 1 Ohm load, supply 75V DC from the power supply and measure voltages at points A, B, C and G with respect to ground, I see a voltage pulse across the load (point B & C) as shown in the oscilloscope image attached. The voltage pulse between B and C is shown with Math channel in red color.
However, I also observe an undershoot at the end of the pulse (Math channel in the image) and some ringing. Can anybody help me explain what may be causing such a large undershoot ? I am expecting voltage difference between B and C to drop to zero once the gate signal (G) is switched off. I am not very much concerned about ringing that follows the undershoot, but I would also like to know ways to minimize it.
Thanks,