Variable Coil Current Control

[ZED]

Heres a cct that i have been playing with,i use the mosfet to regulate the current flow and an opamp to drive the gate,the fet is hard on until there is 3 amps in the coil then the fet holds it there till end of transmit.
From memory the gate voltage is between 4 to 5 volts during regulation,the opamp goes rail to rail with switch on and switch off.
Except for the fet getting hot the cct works very well.The transmit width is 300 u/sec and freq is 1khz,will be trying diff fets over time to see if i can get one that runs a bit cooler.
Tryed many opamps to drive the gate,most cant handle it.

Zed

[Tinkerer]

Heres a cct that i have been playing with,i use the mosfet to regulate the current flow and an opamp to drive the gate,the fet is hard on until there is 3 amps in the coil then the fet holds it there till end of transmit.
From memory the gate voltage is between 4 to 5 volts during regulation,the opamp goes rail to rail with switch on and switch off.
Except for the fet getting hot the cct works very well.The transmit width is 300 u/sec and freq is 1khz,will be trying diff fets over time to see if i can get one that runs a bit cooler.
Tryed many opamps to drive the gate,most cant handle it.

Zed

Very interesting.
What does the charge current ramp look like?

Tinkerer

[ZED]

Tinkerer it looks almost identical to this pic but this pic is from a different cct and also it was running on a 6 volt battery,the current cct usus 12v so the current climbs a bit faster,from memory this cct reachs 3 amps in 100 to 150 u/secs.

Zed

[Tinkerer]

Tinkerer it looks almost identical to this pic but this pic is from a different cct and also it was running on a 6 volt battery,the current cct usus 12v so the current climbs a bit faster,from memory this cct reachs 3 amps in 100 to 150 u/secs.

Zed

Thanks for posting.
I understand that you use the long flat top for experimenting with ground effects?

Tinkerer

[ZED]

Thanks for posting.
I understand that you use the long flat top for experimenting with ground effects?

Tinkerer

In a nut shell yes,the prevous cct had its short comings which promted me to try another cct [the one posted]
I haven`t taken the newer cct for a run yet still more to do,i wanna try a new ground cancling cct.

Zed