So heres the deal,
I have been designing several circuits which require pulse power. To do this I obviously chose mosfets as the switch of choice. I could use 555s, or many other PWM chips to accomplish my goal in driving the mosfet, however it is tedious to measure the duty cycle and the frequency every time I need to make an adjustment, which is alot since I am working with ressonance of tank circuits.
So I thought, perhaps I could use my signal generator to run the mosfet (ir510), but I was worried that having one source for the sig gen (mains power) and one source for the circuit to be driven (18v 3amp power supply) I would possibly damage the signal generator. After a bit of searching I found a Youtube video, where a man used the negative side of the sig gen connected to the gate of the MOSFET and had the source connected to the other two leads with the load inbetween as standard. At first this seemed a bit odd to me, since there is no completed circuit with the sig gen since only the negative lead is connected, and neither source has a common ground.
So I tried it and it worked, I suppose its a sort of capacitive coupling like with one wire power transmission. But.........its opperation was wierd. For example I was testing it with a small dc motor. For starters, the motor would only run when the frequency neared 3Mhz, which would make sense if it was a capacitive deal with the gate. I would think that if it were opperating correctly, I could turn it down to 1hz and have it go on for a sec and off for a sec....not so. Also, when I turn down the potential of the signal generator, the motor slows down, and when I turn it up it speeds up, which is more consistent with a transistor, but weird for a mosfet. so....
1) WHATS HAPPENING!?!?!
2) is there a safe way to run a mosfet with a signal generator without ruining the sig gen? if so please proceede to question 3.
3) Would anybody be willing to draw me up a simple little circuit?
I have been designing several circuits which require pulse power. To do this I obviously chose mosfets as the switch of choice. I could use 555s, or many other PWM chips to accomplish my goal in driving the mosfet, however it is tedious to measure the duty cycle and the frequency every time I need to make an adjustment, which is alot since I am working with ressonance of tank circuits.
So I thought, perhaps I could use my signal generator to run the mosfet (ir510), but I was worried that having one source for the sig gen (mains power) and one source for the circuit to be driven (18v 3amp power supply) I would possibly damage the signal generator. After a bit of searching I found a Youtube video, where a man used the negative side of the sig gen connected to the gate of the MOSFET and had the source connected to the other two leads with the load inbetween as standard. At first this seemed a bit odd to me, since there is no completed circuit with the sig gen since only the negative lead is connected, and neither source has a common ground.
So I tried it and it worked, I suppose its a sort of capacitive coupling like with one wire power transmission. But.........its opperation was wierd. For example I was testing it with a small dc motor. For starters, the motor would only run when the frequency neared 3Mhz, which would make sense if it was a capacitive deal with the gate. I would think that if it were opperating correctly, I could turn it down to 1hz and have it go on for a sec and off for a sec....not so. Also, when I turn down the potential of the signal generator, the motor slows down, and when I turn it up it speeds up, which is more consistent with a transistor, but weird for a mosfet. so....
1) WHATS HAPPENING!?!?!
2) is there a safe way to run a mosfet with a signal generator without ruining the sig gen? if so please proceede to question 3.
3) Would anybody be willing to draw me up a simple little circuit?