Question

A diode detector is used to detect an amplitude modulated wave of 60% modulation by using a condenser of capacity 250pF in parallel with a load resistance 100 kilo ohm. Find the maximum modulated frequency which could be detected by it.

• A. 10.62 $kHz$
• B. 5.31 MHz
• C. 5.31 $kHz$
• D. 10.62 MHz

Answer 1

The correct option is C 5.31 $kHz$

We know that the frequency will be given by:

$f=\frac{1}{2\pi \mu \tau }$

For a combination of resistance and capacitance, $\tau =RC$

Therefore, frequency can be given as:

$f=\frac{1}{2\pi \mu RC}$

So, $\mu =0.6,R=100K\Omega ,C=250\times {10}^{-12}F$

$f=\frac{1}{9.42\times {10}^{-5}}=10.61KHz$