# Inductive kick/spike without overshoot

#### Riccardo Anzil

Joined Oct 16, 2019
4
Hi,
I am trying to have a nanosecond-rise spike across an inductor as shown in the picture below.
I tried with a mosfet to ground (coil between 6V and mosfet's drain) but I get a lot of ringing before the line stabilises to 6V. That is the case even keeping the traces extremely short and large and using all smd parts (to minimise parasitic inductance) etc.
Any ideas/suggestions? Even a completely different circuit would do. All I care is to recreate that fast rising (nanosecond) pulse.
Thanks
Rico

#### Riccardo Anzil

Joined Oct 16, 2019
4
Thank you Albert,
I read through it but I am not sure how that would work. With ref to that circuit, are you thinking to connect my coil between ground and the line marked as output? I don't think that would work?
Perhaps I am missing something or maybe I did not explain myself completely. What I am interested in is to generate an extremely fast (nanoseconds) changing magnetic field across my coil. Whichever circuit can accomplish that I don't really care. All I care is the magnetic field generated by the coil.
Could you please explain your suggestion and/or any others you might have?
Many thanks
Rico

#### Riccardo Anzil

Joined Oct 16, 2019
4
By the way, the coil can inductance can vary between 100uH to 100mH. I can choose but the value has to be in that range.
Thank you again

#### AlbertHall

Joined Jun 4, 2014
10,542
Have you done the maths for ns rise times in a 100mH inductor? t=L/R

#### Riccardo Anzil

Joined Oct 16, 2019
4
That's why I think the only way would be to disconnect the coil suddenly without a freewheeling diode and relying on the sudden voltage raise and subsequence collapse of the magnetic field. It works and I can see it on the scope. But it has lots of ringing before settling to the 6V, but in the picture you can see it decays smoothly into the 6.2V (but I don't have access to that circuit/PCB).
That waveform I posted is from a 97mH coil.
Any ideas/suggestions?

BTW, I noticed your profile picture. Do u race single seaters? I used to for few years.

#### AlbertHall

Joined Jun 4, 2014
10,542
BTW, I noticed your profile picture. Do u race single seaters? I used to for few years.
My picture is me enjoying an 'experience day' at Brands Hatch. Very enjoyable it was too

#### ci139

Joined Jul 11, 2016
1,696