Electronic – How to remove turn on ringing/overshoot in MOSFET output for 1 MHz and 70V Switching

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I have to make a pulse generator square wave for ultrasonic transducer with frequency 1 MHz and 70V for the amplitude, the input is function signal generator with 10V VPP output and 1 MHz. I have made it and it works, but there is a problem. There is always a ringing or overshoot in turn on or rise time but not for the fall. It happens for all frequency, not just in 1 MHz, in 100 KHz for an example, the overshoot is so tight or narrow. this is the circuit that i made

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and this is the result of the output

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what i have done
1. try to add resistor 1M or 10K in gate of MOSFET, the result : no output signal
2. Add Decoupling capacitor, the result : no effect

UPDATE

how i add up the resistor

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So, how to fix the overshoot or the ringing of the output?

Thank you

Best Answer

what i have done 1. try to add resistor 1M or 10K in gate of MOSFET, the result : no output signal

You've done that what you shouldn't do! If you check the datasheet then you'll see that the input capacitance, \$C_{iss}\$, is quite high: 2.16nF. A 1M gate stopper resistor plus this capacitor will form a nice low-pass filter having a cut-off frequency of \$f_C=1000/(2\pi \cdot 2.16 \cdot 1) = 73.7Hz\$, so the input pulses will be totally chopped off thus the MOSFET will never turn on. That's why you get no output.

Cure: Remove 100k and change 1M to a resistance so that it forms a LPF having a cut-off frequency of at least \$3 \cdot f_{SW} = 3MHz\$.

  1. Add Decoupling capacitor, the result : no effect

Of course! Any inductance causes ringing. Where do you have inductances? Answer: Cables and internal drain inductance of the MOSFET.

Cure: A snubber network across Drain and Source/GND. You can find a lot of info about snubber design on Internet.

PS: Your MOSFET does not seem to be suitable for switching at 1 MHz. You should use another like this one (I picked this one randomly. You select according to your voltage and current needs).