Hi,
I would like to make the resonance in this low pass filter circuit (first image) voltage controlled. The resonance is controlled by the pot in the top right. I'm quite new to this but I understand that the voltage on the MOSFET's gate will affect the amount of current that can pass from drain to sink, so it seems an appropriate way to do this. It also seems a cheaper and simpler option than using an optocoupler.
I tried replacing the pot it in a simulator but got errors (second image). Is this an issue with the simulator, or will the circuit actually not work?
Assuming it would work, is it only the gate voltage that will affect the MOSFET's resistance or are there other factors? As I'm looking to replace a pot, I would like to know what the maximum resistance of the MOSFET would be, i.e. when the gate voltage is at maximum. I'm aiming for 100k, but looking at the datasheet for the 2N7000 MOSFET, I don't see it's electrical characteristics expressed like this at all.
Have I misunderstood it by thinking in these terms, or is it possible to convert from the figures in the datasheet to an equivalent resistance at maximum gate voltage, like the rating on a potentiometer?
Thanks,
Ogg
I would like to make the resonance in this low pass filter circuit (first image) voltage controlled. The resonance is controlled by the pot in the top right. I'm quite new to this but I understand that the voltage on the MOSFET's gate will affect the amount of current that can pass from drain to sink, so it seems an appropriate way to do this. It also seems a cheaper and simpler option than using an optocoupler.
I tried replacing the pot it in a simulator but got errors (second image). Is this an issue with the simulator, or will the circuit actually not work?
Assuming it would work, is it only the gate voltage that will affect the MOSFET's resistance or are there other factors? As I'm looking to replace a pot, I would like to know what the maximum resistance of the MOSFET would be, i.e. when the gate voltage is at maximum. I'm aiming for 100k, but looking at the datasheet for the 2N7000 MOSFET, I don't see it's electrical characteristics expressed like this at all.
Have I misunderstood it by thinking in these terms, or is it possible to convert from the figures in the datasheet to an equivalent resistance at maximum gate voltage, like the rating on a potentiometer?
Thanks,
Ogg
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