Question

Consider the circuit shown in the figure below:



An ideal DC current source is connected to a resistor R through a diode D. the diode D can be replaced by its piecewise linear model when it is forward biased, in which the diode can be modeled as a battery of 0.7 V in series with a forward resistance of 10 $\Omega$. If the voltage drop across the current source is measured as 10 V, then the value of load resistance R is equal to _____ $k\Omega$

Answer 1

By replacing the diode with its equivalent model, we get,



Now, $R=\frac{V_0}{I_0}$

$V_0=10-0.7-10\times 5\times {10}^{-3}$

$V_0=9.25V$

and $I_0=I_{in}=5mA$

$\therefore R=\frac{9.25}{5}\times {10}^3$

$=1.85k\Omega$