# How to step up voltage?

Discussion in 'General Electronics Chat' started by wes, Mar 10, 2011.

1. ### wes Thread Starter Active Member

Aug 24, 2007
242
2
Hello, I am going to be building a circuit that will be operating at high voltages
( about 100kv or so). The problem is I need to be able to switch it off quickly (about 1 nanosecond and under). Since the switching times are faster then any relay I know could handle, I figured I would end up using transistors controlled by a pulse generator. The problem is I can't have the transistors directly controlling the voltage as they would just short circuit. So What I thought about doing was dividing the voltage using a voltage divider down to a reasonable range of about 100 volts, then having the transistor control the low voltage but I just don't know how to step the voltage back up to 100 kv afterwards

Does anyone know how to, or maybe a better way of doing it without the voltage divider. I just need to be able to have a switching time of 1 nanosecond and under, So from off to full on in about 1 nanosecond.

2. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
You may have a bit of trouble getting there, 1 nanosecond is awful fast. Add the voltage to it and it becomes a real challenge. I'll be following this thread with interest.

3. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
Let's see, switching 100kV @ 1GHz.

Mind telling us why you think you need that high of a voltage, switched that quickly?

In the meantime, an LT1016 ultra fast comparator has a 10nS propagation delay time; and that's switching signals at logic levels.

Meanwhile, 100kV can ionize the air and jump a gap of ~1.31 inches at sea level. You're probably not going to break that arc without something like a knife switch from an old Boris Karloff movie, or contacts in oil - and your switching times would be very slow; hundreds of ms at best.

Also, 100kv can be extremely hazardous. We usually don't discuss such high voltage items unless it's purely theoretical.

4. ### Kermit2 AAC Fanatic!

Feb 5, 2010
3,849
965
motor driven mechanical commutators just sprang to mind.

Tesla used such things and he achieved very high freq AC transformer linkages.

I don't think any of us are in his 'league' when it comes to the mad scientists stuff though. Better off choosing something slightly less dangerous and cheaper to build.

5. ### wes Thread Starter Active Member

Aug 24, 2007
242
2
I just had a quick idea, Would it be possible to set it up using a a bunch of transistors connected in series with some resistors. So that way I can control a high voltage of maybe 1000V with say 10 100v Transistors. Which would be operated by a timing circuit.