I need something that switches on/off faster than relays. Will some boolean gates and transistors do the trick?

Thanks!
Lac.

I need something with EXACTLY the same properties as a relay. When power flows to A, power goes from B to C, and when there ain't any power going to A, no power will go from B to C either. Think you get the point.

Thanks!
Lac.

Its depended in what current\voltage you need to switch on\off and in what frequency.

You can use a simple transistor or MOSFET transistor for switching.

I also find out recently a very nice IC (LCA110) by "Clare", they are calling it "MOSFET Relay".
Basicly its a very nice optcoupler that can manage 350V/120mA in its load and works like a true relay.

Simple +12VDC, and don't think about the freq. it is maybe goning switch once a week or something odd like that.

Cheers!
Lac.

Yes a solid state relay will couse a voltage drop higher than a transistor but again it depends on the application you are designing

Heres a simple NPN transistor switching sample.
When the 5kohm resistor will get a 5V input it will output 12v.

Why does the resistors have to be such a high resistance? to protect the transitor?

Cheers!
Lac.

what kind of circuit do you intend to use it for?

Lac, a 4066 cmos quad bilateral switch may be what you are after.
It's a chip with 4 switches, that will work similar to 4 indipendent relays.( if you wire it up properly).

Why does the resistors have to be such a high resistance? to protect the transitor?

no, the resistors have such a high resistance so as to keep it deep into saturation. no matter what the input voltage the circuit will act as a switch. but this is not the kind of switch u need. this is a digital switch. u need an analogue switch. a solid state relay or an SCR should be your choice. what are your current requirements. and when u say simple 12VDC what do u mean. is that the voltage that is going to trigger the switch or is it the voltage that is going to be triggered.

ok, sorry for being in a hurry there.

I'm having this digital-clock-circuit that will usally be plugged into the wall, but when I disconnect it from the wall (to move it to a new location or something like that) I want the clock to keep on running (so the time is always ticking, and I don't need to set the time each time I have disconnected it from the wall)

To be able to do this I need some kind of backup power, in this case a 7.2V battery. So what I want to do, is that when the power from the wall is disconnected the battery will kick in. I have tried this with a relay, but the time it takes to switch it from "wall-power" to "battery-power" is much to long, since this is a digital clock the time will be EXACT at all times, and therefore I can't allow it to be a little delay when the clock is disconnected and/or disconnected

So what I simply need is a way to switch between the two power sources, in no time, dependent if power is coming from the wall's 12VDC or not.

The freq. that it will be switching is dependent on how often it will be moved around my house, and I don't think that will be more often than mostly once a week.

Cheers! I Hope I made myself a little more intelligible now :wink: .
Lac