Comparisons With The Triode
- Pentodes (and tetrodes) tend to have a much lower feedback capacitance, due to the screening effect of the second grid.
- Pentodes tend to have a higher noise (partition noise),
- Triodes have a lower internal anode resistance, and hence higher damping factor when used in audio output circuits, compared with pentodes, when negative feedback is absent. That also reduces the potential voltage amplification obtainable from a triode compared with a pentode of the same transconductance, and usually means a more efficient output stage can be made using pentodes, with a lower power drive signal.
- Pentodes are almost unaffected by changes in supply voltage, and can thus operate with more poorly stabilized supplies than triodes. An examination of the characteristics shown here will show that the plate current hardly changes as plate voltage varies.
- Pentodes and triodes (and tetrodes) do have essentially similar relationships between grid (one) input voltage and anode output current when the anode voltage is held constant, i.e. close to a square-law relationship.
Read more about this topic: Pentode
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“I don’t like comparisons with football. Baseball is an entirely different game. You can watch a tight, well-played football game, but it isn’t exciting if half the stadium is empty. The violence on the field must bounce off a lot of people. But you can go to a ball park on a quiet Tuesday afternoon with only a few thousand people in the place and thoroughly enjoy a one-sided game. Baseball has an aesthetic, intellectual appeal found in no other team sport.”
—Bowie Kuhn (b. 1926)