Voltage amplifier stages having the characteristics show in the following table are available. The signal source has an open-circuit voltage of 20mV rms and an internal resistance of 2MΩ. The load is a 20Ω resistance. Design a cascade amplifier using smallest number of stages that provides at least 1 W to the load. What are the values of the input resistance, the output resistance and the open-circuit voltage gain of your amplifier?
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Amplifier stage type
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Open circuit Voltage gain
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Input Resistance
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Output Resistance
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A
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1
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10 MΩ
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1 kΩ
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B
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5
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1 kΩ
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1 Ω
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C
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10
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20 kΩ
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100 Ω
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