Question 179: Semiconductors and Logic Gates

Question

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

Accepted Answer

Given : Resistance $$R=100$$ kilo $$ohm=100$$ $$ 	imes {10^3}\Omega $$
$$	herefore$$ Capacitance $$C=250$$ picofarad $$ = 250 	imes {10^{ - 12}}F$$
$$	au  = RC = 100 	imes {10^3} 	imes 250 	imes {10^{ - 12}}\,\sec $$
$$ = 2.5 	imes {10^7} 	imes {10^{ - 12}}\sec $$
$$ = 2.5 	imes {10^{ - 5}}\sec $$
The higher frequency which can be detected with tolerable distortion is
$$f = {1 \over {2\pi {m_a}RC}}$$
$$ = {1 \over {2\pi  	imes 0.6 	imes 2.5 	imes {{10}^{ - 5}}}}Hz$$
$$ = {{100 	imes {{10}^4}} \over {2.5 	imes 1.2\pi }}Hz$$
$$ = 10.61KHz$$
This condition is obtained by applying the condition that rate of decay of capacitor voltage must be equal or less than the rate of decay modulated signal voltage for proper detection of modulated signal.

Answer

$$10.62$$ $$MHz$$

Answer

$$10.62$$ $$kHz$$

Answer

$$5.31$$ $$MHz$$

Answer

$$5.31$$ $$kHz$$

Semiconductors and Logic Gates

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

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