Vacuum Tubes Objectives Part 03
41 . In a triode , the third electrode is kept near the cathode
42 . The grid of a triode is normally maintained at a negative potential with respect to cathode
43 . The transfer characteristics of a triode Is a relation between grid voltage and plate current for constant values of plate voltage
44 . The characteristics of a triode between grid value and plate voltage for constant value of plate current is known as constant current characteristics
45 . When the cathode of vacuum tube is heated and anode is not connected to any external circuit electrons from a space chargeQuestion 46 to 48 refer to fig. 12.The V-I characteristic of a diode are shown in fig.12
46 . The space charge limited current exist between O AND D
47 . All emitted electrons are collected by the plate beyond D
48 . The space-charge limited current is given by the relation ip=k vp^3/4
49 . In a diode the plate current increase when the plate voltage is made more positive
50 . A triode can also be used as an amplifier because any small change in grid voltageis capable of causing a larger change in plate voltage
51 . In a vacuum diode cathode emits electrons and the plate voltage is positive with respect to cathode
52 . In a cathode ray tube, anode electrode has the highest positive voltage
53 . The characteristics of triode shown in fig.13 is known as static plate characteristics
54 . For a triode the ratio of a small change in plate current to the charge in grid voltage producing it, when plate voltage remains constant, is known as mutual conductance
55 . The mutual conductance of triode is usually expressed in terms of mili-seimens
56 . The mutual conductance of a triode is usually in the range 1 to 10 ms
57 . For a triodethe characteristic between plate voltage and plate current for constant value of grid voltage is known as static plate characteristics
58 . represents the amplification factor for a triode Δip/Δvg (Ip constant)
59 . The unit of amplification factor are it is dimensionless
60 . The amplification factor for a triode usually range from 15 to 100
