For a CE- transistor amplifier , the audio signal voltage across the collector resistance of ` 2 k Omega ` is 2 V . Suppose the current amplifiaction factor of the transistor is 100 . Find the input signal voltage and base current , if the base resistance is `1 k Omega` .

Answer

A, B

Explanation

For give amplifier,
` V_0 = 2V , R_0 = 2 k Omega`
` beta _(ac) = 100, R_i = 1 k Omega `
We have, output voltage , `V_0 = 1_C R_0 `
` rArr I_C` = collector current
` = V_0 / R_0 =2/ ( 2 xx 10^(3)) = 10^(-3) A `
` = 1 mA`
Also , current amplication ` beta = i_C / i_B `
` rArr i_B = i_C/ beta = 10^(-3) / 100 A `
` = 10^(-5) A = 10 xx 10^(-6) A `
` = 10 mu A `
and voltage amplification
` A_V = (beta R_0) / R_i = V_0 / V_i `
` rArr V_i = (V_0 R_i) / (beta R_0) = (2 xx 1 xx 10^(3)) /( 100 xx 2 xx 10^(3)) `
` = 10^(-2) "volts" = 10m V`