I need a switching element which would have low voltage drop on it

**broken link removed**

I want to design a circuit as in the picture.

I want to sence a voltage signal (x(t)) which can vary from 0V to 5000V. The signal will be driven to a MCU unit whose maximum input voltage can be 5V. I want to divide this input voltage using voltage dividers if the voltage level is greater than 5V.


But to this, I need four switching elements for switching on and off these four voltage dividers. To keep the sensitivity of the circuit high, these switching elements must have as low voltage drop as possible on them. In the schematic above, I placed four FET transistors for this purpose, but I'm not sure if I made the correct choice. As you guess, the swithcing element will work only in cut-off and saturation modes. FETs have lower internal impedence that BJTs, so they are more convenient for my project, isn't it? Is there any other semiconductor element you can suggest, which would have less voltage drop on it? I think old mechanical relays are best for this, but their response time is longer, they keep more space on the board, and I don't want any non-solid-state circuit elements on my circuit.

Have any ideas or suggestions?

You can't get a voltage drop much lower than using a FET, I don't know if Mosfets would be a better choice or if Jfets would work adequatly, you'll need to shop around for a FET that has an extremely low RDSon value and still meets any other requirements you might have.

Your circuit requires a FET that will withstand 5000V and there is no such transistor. You would also need gate voltages on the transistors equal to the voltages your are measuring.

You may have to use relays to switch such a high voltage. Make sure the relays are rated for 5000V.

And you need circuit protection in case 5000V is accidentally applied when the circuit is set to the 5V setting.

Also in your circuit, the voltage dividers must include the input resistance of the op amp circuit which is 1kΩ. You are using an inverting configuration which will give you negative output voltages for positive inputs. Use a non-inverting (follower) configuration, which will also give a high input impedance and not load the voltage dividers.

The circuit will dissipate significant power at the high voltages. 5000V generates 2.5W in a 10MΩ resistor. You want to use higher resistor values for the high voltages (or several 10MΩ resistors in series).