I am currently working on using a frequency generator to switch a mosfet.
I have been working on getting this to work for quite sometime now, and I feel I am getting closer and closer. I feel I am missing a fundamental part of how AC and Mosfets operate and this is my problem.
Here is more background on my project. Feel free to skip directly to my questions if you would like.
As viewed from my oscilloscope, my freq generator is putting out a ~1kHz triag wave with these attributes: Vmin=-4.08 Vmax=3.04 RMS=2.32 Vdc=0
or a sine wave with Vmin=-2.48 Vmax=2.32 RMS=1.6 Vdc=0
Please tell me what other attributes compose a wave other than these, if any.
Originally I was trying to run the mosfet off of the sinewave, I am using a IRF510A. The datasheet lists Vth as 2-4V. Since it was not working I tried using a dc biais to bring up the max a bit. No luck.
Tried using trig wave. Used many different bias and resister configurations. No luck.
AC questions:
What happens when an AC current is biased where its min is above 0v?
If the signal is Vmin=0v to Vmax=5v. Is this AC? does the potiential of the dc and the potential of the negative swing of the ac cancel each other out leaving only a net movement forward? Not AC but still sine wave?
Mosfet:
What is the proper way to bias a mosfet? If i understand correctly, even if I have a 1v ac signal, I can bias a 3v Vth mosfet at 3v and the the combined signal of 2-4V will switch the mosfet. What am I missing?
Do I need to take into account any charging of the gate capacitor?
While writing this, I have thought of some issues that I have overlooked. The threshold of the mosfet is 2-4V but it doesn't pass 1A until 5V. I remember now that mosfets are current controlling devices and that even if I hit the 3V threshold, I will not get the current I am wanting. So my next question is will I always see the waveform on the mosfet? Even if I don't pass or get near the threshold, its possible that I will see the waveform no matter what.
How does this work if I am using a 20v on the drain of the mosfet? Should I not see this potential also, just no current is flowing?
I have read alot lately on mosfets but the pieces are just not falling in place yet. I'm sorry for the rambling post.
Project details:
Design a circuit using a frequency generator(5v) to control a mosfet switching 20V@1amp into an inductor. Purpose is to determine resonance frequency of the inductor and feed that frequency into it. First step is to design the oscillator circuit. Next obstacle is determining how the inductor will interact with the frequency fed into it. Will the frequency shift? How do I handle this?
Thank you in advance for any help.
I have been working on getting this to work for quite sometime now, and I feel I am getting closer and closer. I feel I am missing a fundamental part of how AC and Mosfets operate and this is my problem.
Here is more background on my project. Feel free to skip directly to my questions if you would like.
As viewed from my oscilloscope, my freq generator is putting out a ~1kHz triag wave with these attributes: Vmin=-4.08 Vmax=3.04 RMS=2.32 Vdc=0
or a sine wave with Vmin=-2.48 Vmax=2.32 RMS=1.6 Vdc=0
Please tell me what other attributes compose a wave other than these, if any.
Originally I was trying to run the mosfet off of the sinewave, I am using a IRF510A. The datasheet lists Vth as 2-4V. Since it was not working I tried using a dc biais to bring up the max a bit. No luck.
Tried using trig wave. Used many different bias and resister configurations. No luck.
AC questions:
What happens when an AC current is biased where its min is above 0v?
If the signal is Vmin=0v to Vmax=5v. Is this AC? does the potiential of the dc and the potential of the negative swing of the ac cancel each other out leaving only a net movement forward? Not AC but still sine wave?
Mosfet:
What is the proper way to bias a mosfet? If i understand correctly, even if I have a 1v ac signal, I can bias a 3v Vth mosfet at 3v and the the combined signal of 2-4V will switch the mosfet. What am I missing?
Do I need to take into account any charging of the gate capacitor?
While writing this, I have thought of some issues that I have overlooked. The threshold of the mosfet is 2-4V but it doesn't pass 1A until 5V. I remember now that mosfets are current controlling devices and that even if I hit the 3V threshold, I will not get the current I am wanting. So my next question is will I always see the waveform on the mosfet? Even if I don't pass or get near the threshold, its possible that I will see the waveform no matter what.
How does this work if I am using a 20v on the drain of the mosfet? Should I not see this potential also, just no current is flowing?
I have read alot lately on mosfets but the pieces are just not falling in place yet. I'm sorry for the rambling post.
Project details:
Design a circuit using a frequency generator(5v) to control a mosfet switching 20V@1amp into an inductor. Purpose is to determine resonance frequency of the inductor and feed that frequency into it. First step is to design the oscillator circuit. Next obstacle is determining how the inductor will interact with the frequency fed into it. Will the frequency shift? How do I handle this?
Thank you in advance for any help.