Question

In space charge limited region, the plate current in a diode is $10mA$ for plate voltage $150V$. If the plate voltage is increased to $600V$, then the plate current will be:-

• A. $10mA$
• B. $40mA$
• C. $80mA$
• D. $160mA$

Answer 1

The correct option is C $80mA$

In space charge limited region, the plate current is given by child's law $i_p=K{V}_p^{3/2}$

Thus, $\frac{i_{p2}}{i_{p1}}={\left(\frac{V_{p2}}{V_{p1}}\right)}^{3/2}={\left(\frac{6000}{150}\right)}^{3/2}=(4{)}^{3/2}=8$

or $i_{p2}=i_{p1}\times 8=10\times 8mA=80mA.$