Given a vacuum tube with 1000 V plate voltage and 127 ma plate current, what is the correct negative grid bias for a Class B amplifier?

Given a vacuum tube with 1000 V plate voltage and 127 ma plate current, what is the correct negative grid bias for a Class B amplifier?

• A. 40 V
• B. 50 V
• C. 30 V
• D. 60 V

Answer: (A)

In a Class B amplifier, the negative grid bias is essential for proper operation, particularly in controlling the conduction of the output stage. To calculate the necessary negative grid bias, one can utilize the relationship between the plate voltage, plate current, and the characteristics of the vacuum tube. When analyzing a Class B amplifier operating with a given plate voltage and current, a common approach is to refer to the "cut-off" bias. At cut-off, the grid voltage is negative enough so that the plate current drops to zero. The bias needs to be set at a level where only half of the input signal causes the tube to conduct, allowing it to handle the audio waveform without crossover distortion. The correct negative grid bias can often be derived from empirical data or tube characteristic curves, usually found in the tube's datasheet. For a plate voltage of 1000 V and a plate current of 127 mA, the negative grid bias typically lies in the range that allows optimal amplification while reducing distortion, often expressed as a specific negative voltage relative to the cathode. In this case, 40 V is a reasonable choice for the negative grid bias in such a configuration because it sufficiently limits the conduction to just sufficient levels to ensure linear operation during the audio waveform's

In a Class B amplifier, the negative grid bias is essential for proper operation, particularly in controlling the conduction of the output stage. To calculate the necessary negative grid bias, one can utilize the relationship between the plate voltage, plate current, and the characteristics of the vacuum tube.

When analyzing a Class B amplifier operating with a given plate voltage and current, a common approach is to refer to the "cut-off" bias. At cut-off, the grid voltage is negative enough so that the plate current drops to zero. The bias needs to be set at a level where only half of the input signal causes the tube to conduct, allowing it to handle the audio waveform without crossover distortion.

The correct negative grid bias can often be derived from empirical data or tube characteristic curves, usually found in the tube's datasheet. For a plate voltage of 1000 V and a plate current of 127 mA, the negative grid bias typically lies in the range that allows optimal amplification while reducing distortion, often expressed as a specific negative voltage relative to the cathode.

In this case, 40 V is a reasonable choice for the negative grid bias in such a configuration because it sufficiently limits the conduction to just sufficient levels to ensure linear operation during the audio waveform's