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For a two stage amplifier, first amplifier has Voltage gain = 20, Input Resistance Rin1=700Ω, equivalent Resistance Req1=1800Ω and Output Resistor Ro1 = 30KΩ. The corresponding values of second amplifier are :25, 80 KΩ, 12 KΩ, 1.2 MΩ respectively. What is the value of equivalent input noise resistance of the given two stage amplifier? a. 2609.1Ω b. 2607.1Ω c. 107.1Ω d. 2107.1Ω |
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Answer» b. 2607.1Ω R1 = Rin1 + Req1 = 700 + 1800 = 2500Ω R2 = (Ro1 Rin2)/ (Ro1 + Rin2) + Req2 = 30 * 80/(30 + 80) + 12 = 40.92KΩ R3 = Ro2 = 1.2MΩ Equivalent input noise resistance of a two stage amplifier is given by Req = R1 + R2/ A21 + R3/ (A21 A22) = 2500 + 40.92 * 103/(20)2 + 1.2 * 106/(20)2(25)2 = 2607.1Ω |
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