Hello!

I need to make a current source to pulse a hollow cathode lamp. The lamp has an ignition voltage of 500 V and a sustaining voltage of around 150 V but the current must be 10 mA. I tried using an N-channel MOSFET but the maximum current it pulses is 6.33 mA. Am I wrong to put the load on the source side? Should there be a resistor between the gate and the source?

 

Am I wrong to put the load on the source side? Should there be a resistor between the gate and the source?

How about this?

 

Thank you for your reply! I forgot to mention that it's a negative voltage and a negative current to be pulsed. Is that possible with this circuit?

 

Thank you for your reply! I forgot to mention that it's a negative voltage and a negative current to be pulsed. Is that possible with this circuit?

Yes, that is possible:

EDIT
Or use optocoupler: