Thanks for both your replies guys, it appears it actually is quite common, I just haven't personally ever come across this before and was a little surprised, another circuit design to add to the memory bank!
hi guys, I recently scoped a cop 3 wire design coil, I was connected to the power feed using my amp clamp on channel A and connected to coil control using test leads on channel B, (luckily I used attenuator - you will see why) I was under the impression that the transistor for the coil was internal ...