Radio Amateur Quiz Canadian License

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Question A-005-002-008

In a grounded grid amplifier using a triode vacuum tube, what would be the approximate B+ voltage required for an output of 400 watts at 400 mA with approximately 50 percent efficiency?

Correct Answer

2000 volts

Explanation

Efficiency = P_out / P_in. So P_in = P_out / Efficiency = 400W / 0.50 = 800W. P_in = V_plate × I_plate (B+ × Plate Current). So V_plate = P_in / I_plate = 800W / 0.400A = 2000 volts.

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