[SOLVED] Switch between two equal-voltage terminals?

[bobsun]

Hello,

I would like to ask a question on switch.

It’s not difficult to make a switch from high voltage to low, such as turning on and off a motor, using a transistor. However, if the purpose is to cut a connection between two “high” voltages, how could that be achieved?



In the attached image above, there is a 5V battery and a capacitor and a resistor. If the switch is connected on, the capacitor will get charged; if it is off, the battery voltage and capacitor voltage would be separated.

If I would like to control the manner how battery charges the capacitor, then it requires that the connection between the positive end of the battery and the upper end of the capacitor be controlled. Transistors could works for switching paths from high to low, but for things like here between two terminals with same or similar voltage level, it seems that transistor cannot do the job. Then how can it be done?

I know using reed could possibly achieve that; but is that reliable for possible millions of switches? Is there any other component to do this?


Bob

 

[FvM]

Single MOSFET or bipolar transistor sare restrcited to switch unipolar voltages. As long as the voltage difference between the switched terminal has always the same sign, transistors can work well. If the voltage difference can have both polarities, two transistors can be combined. This is most simple with MOSFET, that can be connected back-to-back. See a photovoltaic solid state relay as an example of a bidirectional switch: http://www.irf.com/product-info/datasheets/data/pvg612a.pdf

 

[bobsun]

FvM,

Thanks for the answer. I am reading the linked PDF.

Bob