MOSFET

[Dr.EM]

Hello. I am essentially looking for a way to convert a changing voltage into a changine resistance. I hear that a MOSFET is required, and after looking at it online, it does sound right.

Basically, I currently have a potentiometer (470k) to adjust a parameter, but I want to be able to modulate that parameter, but at higher speed than I can turn the control knob back and forth. The current through the 470k is always very low.

I want the modulation source to be a 555 oscillator going through an integrator to rectify it into a triangular wave. The varying voltage should be from 0-5 volts i'm guessing.

For those who want to know, this is an idea for an LFO on an oscillator.

Can anyone suggest a suitable MOSFET? Cheers.

 

[FRIED]

I think a JFET is what you need. Hard to say without a circuit.

 

[chemelec]

Yes, a JFet.
MPF102 is a good Choice.
But I Think you will need to Change that Voltage range Downward a Bit, with a Resistor Divider.

 

[Dr.EM]

Cool, cheers! I'll try to get hold of those MPF102s, but can't find any JFETs on rapidelectronics.co.uk.

They have MOSFETs and FETs :?

 

[FRIED]

FETs
**broken link removed**

 

[Dr.EM]

Thanks, can't find that number there, are there any there that are suitable?