MONOCOIL SUCCESS

[moodz]

..blocker for negative going flybacks.

... on the subject of blockers and if you have a negative flyback pulse for alternate circuit topologies there is the circuit below however P Mosfets are usually not available in high breakdown voltages.

moodz

[Aziz]

Hi moodz,

be careful, when using the (internal) semiconductors of LTspice library!!!!!!!
The diodes, mosfets (and transistors) didn't implement the break down behaviour (and very likely the other parameters as well).

Use the part's individual and specified spice model from the part's manufacturer in this case.

Cheers,
Aziz

[moodz]

Thanks Aziz ... I am wary of sims ... I did build and test this circuit before I simmed it and managed to get it up to 800 volts before I blew the mosfet up ( which was supposedly rated at 600 volts ).

moodz.

[WM6]

Thanks Aziz ... I am wary of sims ... I did build and test this circuit before I simmed it and managed to get it up to 800 volts before I blew the mosfet up ( which was supposedly rated at 600 volts ).

moodz.

Hi moodz, do you need to change something in code or last version is applicable here too?

[Aziz]

Hey, what's up?

I couldn't verify the spice simulation results however (schematics from post 14 http://www.geotech1.com/forums/showp...1&postcount=14 ). I'm sure, I didn't make anything wrong. I have used the real spice models (IRF740) rather than the internal ones from the library.
???
Aziz

[moodz]

Hey, what's up?

I couldn't verify the spice simulation results however (schematics from post 14 http://www.geotech1.com/forums/showp...1&postcount=14 ). I'm sure, I didn't make anything wrong. I have used the real spice models (IRF740) rather than the internal ones from the library.
???
Aziz

Aziz ... are you sure your library models are working OK ..... add on libraries sometimes dont work because they dont model underlying ideal device behaviour correctly.

Anyway here is the file ... make sure you run the sim till the voltage reachs 16 volts on C1 ( stable operating condition ).

Dont forget .. I ran this on the "real" simulator .... using real parts in a real circuit

moodz

MONODIFF_SIM.zip

[moodz]

Hi moodz, do you need to change something in code or last version is applicable here too?

WM6 are you talking about the UNIPI code for the control chip ?? I did not change the code.

But I did try differenty types of Mosfets in the circuit and they all work ... they just have different maximum break down voltages.

The highest breakdown reached 1700 volts but this is not practical.

moodz.

[moodz]

just to be clear ....

Output of blocker and TX gate pulse

The Simulation result .....


And the result using real devices ( IRF740 etc etc )

[6666]

Thanks Mr Moodz
this is great info
cheers
6666

[Aziz]

Aziz ... are you sure your library models are working OK ..... add on libraries sometimes dont work because they dont model underlying ideal device behaviour correctly.

Anyway here is the file ... make sure you run the sim till the voltage reachs 16 volts on C1 ( stable operating condition ).

Dont forget .. I ran this on the "real" simulator .... using real parts in a real circuit

moodz

[ATTACH]17711[/ATTACH]

Hi moodz,

ok, I have ran the sim much longer so the gate voltage stabilizes at 16 V. In this case, it works.
But the blocking fet circuit needs further improvements.

Aziz

[Midas]

Target shots! Ra! Ra! Ra! Ra!

Thanks Moodz, looks awesome. Not to be greedy but is there any chance you could post some target scope shots to get an idea how well this actually works? Ideally uber small gold since that seems to be the main reason people strive for superfast sampling, but hey whatever you have handy would still be interesting.

[moodz]

Thanks Moodz, looks awesome. Not to be greedy but is there any chance you could post some target scope shots to get an idea how well this actually works? Ideally uber small gold since that seems to be the main reason people strive for superfast sampling, but hey whatever you have handy would still be interesting.

Hi Midas and thanks .. I am caught up with end of year stuff at the moment ... the aim of this circuit is mainly to reduce EMI ... the faster sampling was a surprise. I would assume that if the noise is removed then the sensitivity can be increased and thus smaller targets.
I will have hook up the amp and demod.

moodz

[mickstv]

Hi Midas and thanks .. I am caught up with end of year stuff at the moment ... the aim of this circuit is mainly to reduce EMI ... the faster sampling was a surprise. I would assume that if the noise is removed then the sensitivity can be increased and thus smaller targets.
I will have hook up the amp and demod.

moodz

Hi Moodz, I should have a chance in the next day to two to try this front end, I'll post up the in air results on the .4gram nugget I have.

I take it I can still use the THAT1510 as the preamp.




Mick

[moodz]

Hi Moodz, I should have a chance in the next day to two to try this front end, I'll post up the in air results on the .4gram nugget I have.

I take it I can still use the THAT1510 as the preamp.




Mick

That would be good ... just make sure you check the blocker is working or you know what will happen to the amp

moodz

[mickstv]

That would be good ... just make sure you check the blocker is working or you know what will happen to the amp

moodz

Sure will, money doesn't grow on trees. I've got a couple of STP9NK50ZFP mosfets that I will try, looking at the specs it has a lower capacitance than the IRF740.



Mick