Switching 0-30+ volts at 1A at around 1kHz

An opamp and LM395? The LM395 is spendy, but is pretty much 'bullet proof'. Don't forget the 5k base resistor.

George H.

For high currents, usually called solid state relay. If you can allow for some turnon delay, gizmos like Clairex LCA715 might work.

If the 30V is a power supply you don't mind tapping, a PMOS power FET as high-side switch can be turned on or off with a variety of techniques. Gate through resistor to +30, source to +30, and just sink a measured current from the gate whenever you want it turned 'on'.

V | - | + .-. | | | | | | out + '-' V +-------------+ - | + .-. | | | | | | | '-' | | | | | |< +-+---+| | |\ .-. | | | + | | G|D '-' | +------+ (created by AACircuit v1.28.6 beta 04/19/05

If I understand you correctly, you need current booster for the signal?

Jamie

My analysis of the LM395 chip that I did for ICE _many_ years ago...

Looks like a nice piece of work. I'd heard they were originally from the same die, but it helps to understand the details. Thanks.

Cheers

Phil Hobbs

=A0 =A0 ...Jim Thompson

=A0 =A0| =A0 =A0mens =A0 =A0 |

=A0 | =A0 =A0 et =A0 =A0 =A0|

=A0|

=A0 =A0 =A0 |

ide quoted text -

Ahh, Thanks Jim! It's going to take me a while to work through that.

I'm pretty ignorant when it comes to transistor level design stuff. I'm still being surprised by diodes. I do love that most of your analysis seems to be based on the simple 'diode equation', that's comforting. (it gives one hope)

George H.

First, thank you for your suggestions.

It was a a bit late when wrote my post, so it was a bit misleading. Luckily I know which way the current always goes, one known end is always positive. So, I can use N-channel fets.

Are solid state relays fast and cheap enough? High cost is a problem.

I'll go thru this later (or earlier) and come back.

Works well for first order analysis. If you adhere to symmetry, as I always do, everything works well... keep in mind that, until ~1980 (18 years of successful IC design already under my belt), I had no access to CAD tools... Algebra served me well. ...Jim Thompson

What is the load, what power supplies do you have available, what is the source of the 1KHz switching signal? When you state abstractions like "I want to connect two points with voltages something between 0 or more and 30 volts and with currents a little less than 1A", you're just asking for trouble. If you knew enough to formulate a reasonable abstraction, you wouldn't be on here asking dumb questions in the first place.

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What type of signal potential are you trying to switch? HV, AC ?

I do understand that you want to do this with a 0..30 volt range trigger signal?

Jamie

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Sorry about this delay, I didn't think there would be answers now. I dont dare to post pictures, I'm already telling too much, sorry.

Voltage I am switching is small, less than 10 volts. But both ends will have continously varying potential to earth, now less than 30V. The same pin is always positive. Now I plan to limit gate voltage with diodes and zeners and so on.

In other words, how to get 1kHz gate voltage to a floating gate with some varying potential to earth. Good fets have max gate voltage of less than 30V, so I cant just ground the gate.

Leif

Pulse transformers? Optoisolators?

Good Luck! Rich

Jamie