A friend of mine was asking about circuit protection for his FETs with an inductive load on it (a solenoid in this case), and was thinking that a TVS diode was better than a Schottky for the case. Sure, when a TVS diode sees something over a certain voltage, it clamps that down hard and it wont go much above the clamping voltage the diode is rated to - sounds pretty good... but I've always used schottky's as my primary protection for this particular scenario (a solenoid going open circuit with one leg still connected to your circuit). In order to prove my case, I made a little board with the V-One to put some diodes on, some with caps, some without to show how it worked in the real world.
Solenoids are found in many real-world devices in the form of relays, water/gas switches, door latch activators and such. Any time you have an electromagnetic field and you take away the circuit, it collapses and the field's energy has to go somewhere, usually a big voltage spike. Motors do exactly the same thing.
The test board has a bidirectional 20v TVS diode (its all I had in the parts bin), a 20V Schottky, and a 40V Schottky. One side had caps (0.1uf for the tvs, 1uf for the 40v, 10uf for the 20v), the other side did not.
This is also a good example of why you need to clamp inductive loads. Photos of the scope sorry, I forgot to bring a compatible USB drive with me (the scope is very specific about what sort of rubbish it will accept... none of the good drives work!)
First up, no protection... this is what happens when the small solenoid has no protection, you max out the scope with >300v p-p spike for about 500us.
Next victim, the TVS diode. It clamps the voltage very nicely to 20v. With the 0.1uF cap decoupling the solenoid the little "buzz" at the start goes away and it becomes a straight line.
Both Schottky diodes are the same. Just a square edge from the 12V drive to ground... no fuss, no broken fets.
The 10uF cap on the Schottky, nice little bleed down of the voltage.
If I was an instructor here (I work at a post-secondary institution, but in the applied research division, not with the students,) the V-One would be a great device to show that simulations do actually work, and to demonstrate how components work to students