Which of the following is NOT associated with a P-N junction?

In the following limiter circuit, an input voltage $${\mathrm V}_\mathrm i\;=\;10\sin\left(100\mathrm{πt}\right)$$ applied. Assume that the diode drop is 0.7V when it is forward biased. The Zener breakdown voltage is 6.8V.

The maximum and minimum values of the output voltage respectively are

Two identical NMOS transistors M₁ and M₂ are connected as shown below. V_bias is chosen so that both transistors are in saturation. The equivalent g_m of the pair is defined to be $$\frac{\partial I_{out}}{\partial v_i}$$ at constant V_out. The equivalent g_m of the pair is

The measured transconductance g_m of an NMOS transistor operating in the linear region is plotted against the gate voltage V_G at constant drain voltage V_D. Which of the following figures represents the expected dependence of g_m on V_G?