When a tube is used as a Class B amplifier what portion of the excitation voltage cycle does plate current flow?
• Amplifier classes (A, B, AB, C) and how they differ in conduction angle • Definition of conduction angle in degrees of the input signal cycle • Relationship between efficiency and portion of the cycle during which plate current flows
• Compare Class A, Class B, and Class C operation: over how many degrees of the input cycle does current flow in each? • Think about whether Class B is exactly half the cycle, more than half, or less than half, compared with Class A (full cycle) and Class C (small portion). • Recall where Class AB fits in relative to Class A and B, and use that to narrow down what pure Class B must be.
• Be clear on that Class A conducts for the entire cycle (all 360°) of excitation. • Know that Class C conducts for much less than half of the cycle. • Use Class AB (between A and B) and Class C (far below 180°) to pinpoint what pure Class B must correspond to in degrees.
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