B
Ben Vaughan
Hi,
I have a very simple MOSFET circuit that is not performing how I
thought it would, I'm hoping someone might be able to tell me what's
happening.
The circuit is as follows: I have a drain resistor of 750 ohms, the
source goes to ground and the gate has a voltage applied directly from
a power supply. I'm using a 2N7000 FET and the supply is as 20V. The
gate voltage I can vary. If I set the gate voltage so that the FET
should be within it's Linear range, say around 2.5V for example, the
output starts at 6.7V and drops at an exponential rate to around 6.22V
and then seems to be fluctuating quite a lot, with 10's of millivolts
change. Also the room temperature is a constant 19 degrees celsius. I
have tried 5 different FET's all with similar results.
I don't understand why this is happening? I have a fixed gate voltage,
fixed supply voltage, fixed resistance, constant temperature and yet
my output is fluctuating by quite a lot. Can someone enlighten me as
to what's happening?
Cheers,
Ben.
I have a very simple MOSFET circuit that is not performing how I
thought it would, I'm hoping someone might be able to tell me what's
happening.
The circuit is as follows: I have a drain resistor of 750 ohms, the
source goes to ground and the gate has a voltage applied directly from
a power supply. I'm using a 2N7000 FET and the supply is as 20V. The
gate voltage I can vary. If I set the gate voltage so that the FET
should be within it's Linear range, say around 2.5V for example, the
output starts at 6.7V and drops at an exponential rate to around 6.22V
and then seems to be fluctuating quite a lot, with 10's of millivolts
change. Also the room temperature is a constant 19 degrees celsius. I
have tried 5 different FET's all with similar results.
I don't understand why this is happening? I have a fixed gate voltage,
fixed supply voltage, fixed resistance, constant temperature and yet
my output is fluctuating by quite a lot. Can someone enlighten me as
to what's happening?
Cheers,
Ben.