A square-law device is one whose output is proportional to the square of the input. A junction field-effect transistor (JFET) is such a device. The current (I) that will flow though an n-channel JFETwhen a voltage (V) is applied as:

I=A(1-v/b)^2

Where A is the drain saturation current and B is the gate source pinch off voltage. Solve this equation for V using the quadratic formula.