Question #191016

Consider the single stage amplifier, values of h-parameters are hie=15kΩ, hfe=(150-X1), hre=15˟10-4 and hoe=50µA/V. Rs=15Ω, Calculate Av, Ai, Ri, Zo and also derive the relations which you used.

Expert's answer

"A_V=\\frac{v_o}{v_s}"

"v_0= \\frac{-h_{fe}}{h_{oe}}I_b \\implies I_b=\\frac{-h_{oe}}{h_{fe}}V_0"

"I_b=\\frac{V_s-h_{re}V_0}{R_s+h_{ie}}"

"\\frac{-h_{oe}}{h_{fe}}V_0(R_s+h_{ie})=v_s-h_{re}v_0"

"v_0(\\frac{h_{re}h_{fe}-h_{oe}(R_s+h_{ie}}{h_{fe}})=v_s"

"\\frac{v_0}{v_s}=(\\frac{h_{fe}}{h_{re}h_{fe}-h_{oe}(R_s+h_{ie}})"

"A_v=(\\frac{h_{fe}}{h_{re}h_{fe}-h_{oe}(R_s+h_{ie}})"

"A_v=\\frac{149}{1.3*10^{-4}+149-50*10^{-6}(0.013+0+1.3)}=7718.46 V\/V"

"A_i=\\frac{I_0}{I_b} \\implies I_0=-hf_eI_b \\implies \\frac{I_0}{I_b}=-hf_eI_b=-149 \\frac{A}{A}"

"R_i{n}=\\frac{V_{in}}{i_b}"

"V_{in}=h_{ie}ib+h_{re}v_0"

"v_0= \\frac{-h_{fe}}{hoe}I_n"

"v_{in}=[h_{ie}-\\frac{h_{fe}h_{re}}{h_{oe}}]I_n"

"\\frac{v_{in}}{I_n}=R_{in}=h_{ie}-\\frac{h_{fe}h_{re}}{h_{oe}}"

"R_{in}=1.3-\\frac{14.9*1.3*0.0001}{50*0.000001}=0.912 k\\Omega"

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