## CHAPTER

THERMIONIC EMISSION THE HIGH-VACUUM THERMIONIC DIODE The operation of the majority of electron tubes is dependent upon thermionic emission. The theory of thermionic emission is therefore of great importance in the study of electron tubes. It is the purpose of this chapter to discuss the basic principles of thermionic emission, the construction of practical emitters, and the flow of electron space current in high-vacuum tubes containing two electrodes. 2-1. Theory of Thermionic Emission....

## 1

Current-voltage characteristic of a typical gas-filled cold-cathode diode. tion, the release of still another secondary electron, the current continues to increase without further increase of voltage. In fact, as shown in Fig. 9-1, the voltage actually falls. The increase of current without increase of voltage is called breakdown, and the voltage at which it commences is called the breakdown voltage. The current that flows just prior to breakdown is called the threshold current. In...

## Methods Of Analysis Of Vacuum Tubes And Vacuumtube Circuits

Since the application of vacuum tubes is governed in part by the extent to which it is possible to analyze the operation of tubes and associated circuits, a study of the methods of analysis is of considerable importance. This chapter will therefore present analytical and graphical methods of analysis of high-vacuum tubes and their circuits. 4-1. The Equivalent Plate Circuit.1 In the solution of many vacuum-tube problems, particularly when the excitation voltage is small and the load impedance...

## Maximum Allowable Plate Current In 6j5

Experimentally determined curves of full power output of a type 45 triode in class A1 operation. 1 Massa, Frank, Proc. I.R.E., 21, 682 (1933) Electronics, September, 1938, p. 20. 1 Seemingly, Eq. (6-27) is in disagreement with Maxwell's rule that maximum power is transferred from a generator to a load when the load impedance is equal to the generator impedance. The student may show, Equation (6-27) may also be derived by an analysis based upon the assumption that the plate...

## T

Temperature, operating of cathodes, 26, 29, 31 Temperature, saturation, 24 Tetrode, 63-66, 266-268 Thermionic emission, 21-34, 251-253 Thermionic tube, definition of, 44 Threshold current, 235 Threshold frequency, 307 Thyratron, 252-292 as an a-c control device, 280-290 applications of, 270 characteristics of, 263-268 comparison with high-vacuum tubes, 268-269 deionization time of, 260-262, 264-265 as a d-c control device, 271-273 electrode structure of, 263-268 grid-control characteristics of,...

## Direct Reading Harmonic Scales Espley

Substituting Eqs. (4-20) and (4-21) in Eq. (4-19) and solving the resulting simultaneous equations gives max I m in - max + - 2Ibo Substituting Eq. (4-22) in the first two terms of Eq. (4-16) and expanding sin2 u> t gives ib Ibo f 1 ( max min 2Ibo) f k(Iu - i( m,s + ,, - 2Ib0) COS 2ut (4-23) The average plate current and the amplitudes of the fundamental and second-harmonic components of plate current are Iba I bo H H 0 r( niai t I min + 2 Ibo) . j Imin 2 bo) It is important to note that Eqs....

## R

J., 178 Ramo, S., 177 Redl, A., 113 Reich, H. J., 155, 156, 157, 178, 218, 235, 243, 259, 363, 368 Reid, D. G., 177 Reimann, A. L., 47 Rhoad, E. J., 176 Richards, L. A., 156 Richards, P. A., 369 Richardson, 0. W 21, 23, 46 Richter, W., 89, 353 Rider, J. F., 364 Righi, A., 243 Risch, R 258 Ritchie, D., 334 Rivlin, R. S 178 Roberts, F., 195 Roder, H., 190, 199, 202, 204, 207, 210, 212, 213 Romain, B. P., 335 Rsehewkin, S., 224 Ruiz, J. J., 364 Runge, I., 275 Ruska, E., 27

## Info

-Curves showing fatigue in the Photronie cell. if an amplifier is used between the cell and the relay. A single-stage amplifier is ordinarily inadequate. Even for small values of flux, for which the voltage sensitivity is high, the Photronie cell has a sensitivity of only about 25 mv lumen, and the Photox cell about 50 mv lumen. This is very small as compared with 1 Bartlett, C. H., Rev. Sci. Instruments, 3, 543 1932 . 2 Lamb, A. H., Instruments, 5, 230 1932 . the 500-volt lumen sensitivity...

## Vwwv

A high-vacuum amplifier tube may be used in place of the resistance in phase-control circuits. By this means a very small direct voltage in the grid circuit of the high-vacuum tube can control large amounts of current and power. Figure 9-49 shows one method of connecting the vacuum tube. The load current can be doubled by the use of two thyratrons in a full-wave circuit such as that of Fig. 9-50a.1 This circuit also illustrates the use of a phase shifter, which may be replaced by a combination...

## AC

Circuits for Use with Modulated Light. To amplify only the varying component of anode current produced by fluctuating or modulated light, as in the reproduction of sound recorded on film, the phototube is usually coupled to the first amplifier tube by means of resistance-capacitance coupling, as shown in p-v Fig. 10-20. The coupling condenser fXi prevents the variation of amplifier bias with changes of average illumina- Fig. 10-20. Circuit for con- tion- After the first stage, any type...

## Ghvacuum Tubes

The greatest single advu vacuum tubes undoubtedly canu De Forest of a control electrode of the diode.1 The principal val arises from the fact that relatively may be controlled by small vari electrode relative to the cathodje ,nce in the development of e with the introduction by between the cathode and plate ue of such a control electrode large plate current and power actions of voltage of the control without the expenditure of Fig. 3-1. Electrode structure of typical filamentary and...

## Transitron Oscillator

Under the threshold condition, when p L rC, Eq. 8-4 reduces to Inasmuch as r, the a-c resistance of the inductance coil and leads, is ordinarily only a few ohms, whereas the negative resistance p is seldom less than 2 or 3 thousand ohms, the frequency is practically equal to l 2x LC, and small changes in p, such as might result from the variation of battery voltages, have a negligible effect upon the oscillation frequency if the threshold condition can be maintained. The current represented by...

## E R

Thus, if the diode were a perfect rectifier having zero resistance, the circuit could be calibrated on direct voltage and used to measure either direct or sinusoidal alternating voltage. Actually, curvature of the diode static characteristic and flow of plate current when the plate voltage is zero, resulting from initial velocity of electrons, cause the ratio of the alternating to the direct voltage reading to depart somewhat from the theoretical value 2.22. The error, which is most pronounced...