The output voltage in the following circuit is (Consider ideal diode case)

$A$ realistic graph depicting the variation of the reciprocal of input resistance $(1/r_i)$ in an input characteristics measurement in a common emitter transistor configuration is:

When a $PN$ junction diode is reverse biased,

In the figure,the potential difference between $A$ and $B$ is......$V$.

The junction diode in the following circuit requires a minimum current of $1 \, mA$ to be above the knee point $(0.7 \, V)$ of its $I-V$ characteristic curve. The voltage across the diode is independent of current above the knee point. If $V_B = 5 \, V$,then the maximum value of $R$ so that the voltage is above the knee point will be:

The ratio of forward bias resistance to reverse bias resistance of a $P-N$ junction is approximately .......