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Figure 1-13.Ep - Ip characteristic curve
Plate Dissipation

Neets Module 06-Introduction to Electronic Emission, Tubes, and Power Supplies
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1-16 You can see from the analysis that the most consistent control of plate current takes place over the linear portion of the Ep - Ip curve. In most applications, electron tubes are operated in this linear portion of the characteristic curve. Plate Resistance (Rp) One tube parameter that can be calculated from values on the Ep - Ip curve is known as plate resistance, abbreviated as Rp. In a properly designed electron tube, there is no physical resistor between cathode and plate; that is, the electrons do not pass through a resistor in arriving at the plate. You may have wondered, however, why the variable dc voltage source of figure 1-12 didn’t blow a fuse. Doesn’t the plate circuit appear to be a short circuit-a circuit without a load to limit the current? The fact is, there is a very real, effective RESISTANCE between cathode and plate. It is not lumped in a resistor, but the circuit may be analyzed as if it is. The plate resistance of a given tube, Rp, can be calculated by applying Ohm’s law to the values of Ep and Ip. Figure 1-14 is a typical diode Ep - Ip curve. The plate resistance has been figured for Rp under three different conditions, as follows: Figure 1-14.—The Ep - I characteristic curve for a diode. Remember that 1 mA = .001 ampere; therefore 40 mA =.040 ampere. Solution: The other two indicated values of Rp were figured in the same way.






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