Voltage controlled current source - is this linear or switching?

Thread Starter


Joined Dec 23, 2009

I found a voltage controlled current source circuit as follows:

Is it a 'linear' or 'switching' circuit? The article mentions that Q1 is a MOSFET. In fact I wish to have a 'linear' type. For the rating shown in figure above, i.e. 150V and 3A, would you please recommend an MOSFET or BJT? The load is inductive and the current is DC current.

Another circuit:

What's about this one? 'Linear' or 'Switching? Why is the feedback connected to non-inverting input of the op-amp?

Thank you very much.
Last edited:


Joined Jul 17, 2007
They are both linear.

I don't know why you'd want to use a linear regulator for an inductive load though. It'll be very inefficient.

Thread Starter


Joined Dec 23, 2009
Hi SgtWookie, thanks for your reply. In fact, the load is the armature winding of a dc machine, which is driven as a generator by another motor. The motor always rotates in the same direction, therefore ILoad generated in the armature winding of the dc machine is uni-directional. I'm aware that a 'linear' type current sink is not efficient, but I wish to have a current sink which will not add ripple to the ILoad. By the way, do you want why one circuit has feedback to inverting input, and another one has feedback to non-inverting input?