Question

An output signal of a power amplifier has amplitudes of 2.5 V fundamental, 0.25 V second harmonic and 0.1 V third harmonic. The total percentage harmonic distortion of the signal is
1. 12.8%
2. 10.8%
3. 6.4%
4. 1.4%

Answer 1

Correct Answer - Option 2 : 10.8%

Given:

A1 = 2.5V, A2 = 0.25V, A3 = 0.1V

\(\begin{array}{l} {D_2} = \frac{{{A_2}}}{{{A_1}}} = 0.1\\ {D_3} = \frac{{{A_3}}}{{{A_1}}} = 0.04\\ THD = \sqrt {D_2^2 + D_3^2 } = \sqrt {{{\left( {0.1} \right)}^2} + {{\left( {0.04} \right)}^2} } \end{array}\)

= 0.1077

= 10.77%