TUBE: KT88
FICHIER SOURCE: sheets/086/k/KT88.pdf
FABRICANT: Genalex / The M-O Valve Company Limited (GEC)
ANNEE: December 1974 (Issue 5)
TYPE DECLARE: BEAM TETRODE

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THE M-O VALVE COMPANY LIMITED — Genalex — KT88 — BEAM TETRODE
BRIEF DATA:
The KT88 has an absolute maximum anode dissipation rating of 42W, designed for output stage of an a.f. amplifier. Two valves in Class AB1 give continuous output up to 100W. Also suitable as series valve in a stabilised power supply.
The KT88 is a commercial version of the CV5220 and is similar to the 6550.
HEATER:
  Vh ........... 6.3 V
  Ih (approx) .. 1.6 A
MAXIMUM RATINGS:                       Absolute   Design Maximum
  Va ................. 800        800        V
  Vg2 ................ 600        600        V
  Va,g2 .............. 600        600        V
  -Vg1 ............... 200        200        V
  Pa ................. 42         35         W
  Pg2 ................ 8          6          W
  Pa+g2 .............. 46         40         W
  Ik ................. 230        230        mA
  Vh-k ............... 250        200        V
  Tbulb .............. 250        250        °C
  Rg1-k (cathode bias):
    Pa+g2 ≤ 35W ... 470 kΩ
    Pa+g2 > 35W ... 270 kΩ
  Rg1-k (fixed bias):
    Pa+g2 ≤ 35W ... 220 kΩ
    Pa+g2 > 35W ... 100 kΩ
CAPACITANCES (Measured on a cold unscreened valve):
Triode Connection:                     Tetrode Connection:
  Cg1-a,g2 ...... 7.9 pF                 Cg1-a ......... 1.2 pF (Cga)
  Cg1-all less a,g2 ... 9.3 pF           Cg1-all less a ... 16 pF (Cin)
  Ca,g2-all less g1 ... 17 pF            Ca-all less g1 ... 12 pF (Cout)

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CHARACTERISTICS:
Tetrode Connected:
  Va ......... 250 V
  Vg2 ........ 250 V
  Ia ......... 140 mA
  Ig2 (approx) 3 mA
  -Vg1 (approx) 15 V
  gm ......... 11.5 mA/V
  ra ......... 12 kΩ
  µg1-g2 ..... 8
Triode Connected:
  Va,g2 ...... 250 V
  Ia+g2 ...... 143 mA
  -Vg1 (approx) 15 V
  gm ......... 12 mA/V
  ra ......... 670 Ω
  µ .......... 8
TYPICAL OPERATION:
Push-Pull. Class AB1. Cathode Bias. Tetrode Connection:
  Va(b) ............ 560 V
  Va(o) ............ 521 V
  Vg2 .............. 300 V
  Ia(o) ............ 2x64 mA
  Ia(max sig) ...... 2x73 mA
  Ig2(o) ........... 2x1.7 mA
  Ig2(max sig) ..... 2x9 mA
  RL(a-a) .......... 9 kΩ
  Rk ............... 2x460 Ω
  -Vg1 (approx) .... 30 V
  Pout ............. 50 W
  Dtot ............. 3 %
  IM ............... 11 %
  Pa(o) ............ 2x33 W
  Pa(max sig) ...... 2x12 W
  Pg2(o) ........... 2x0.5 W
  Pg2(max sig) ..... 2x2.7 W
  V(g1-g1)(ac) crest 60 V

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Push-Pull. Class AB1. Fixed Bias. Tetrode Connection:
  Va(b) ............ 560 V
  Va(o) ............ 552 V
  Vg2 .............. 300 V
  Ia(o) ............ 2x60 mA
  Ia(max sig) ...... 2x145 mA
  Ig2(o) ........... 2x1.7 mA
  Ig2(max sig) ..... 2x15 mA
  RL(a-a) .......... 4.5 kΩ
  -Vg1 (approx) .... 34 V
  Pout ............. 100 W
  Dtot ............. 2.5 %
  IM ............... 10 %
  Pa(o) ............ 2x33 W
  Pa(max sig) ...... 2x28 W
  Pg2(o) ........... 2x0.5 W
  Pg2(max sig) ..... 2x4.5 W
  V(g1-g1)(ac) crest 67 V
Push-Pull. Class AB1. Cathode Bias. Ultra-Linear Connection (40% Tapping Points):   (col1 / col2)
  Va,g2(b) ......... 500 / 375 V
  Va,g2(o) ......... 436 / 328 V
  Ia+g2(o) ......... 2x87 / 2x87 mA
  Ia+g2(max sig) ... 2x99 / 2x96 mA
  RL(a-a) .......... 6 / 5 kΩ
  Rk ............... 2x600 / 2x400 Ω
  -Vg1 (approx) .... 52 / 35 V
  Pout ............. 50 / 30 W
  Dtot ............. 1.5 / 1 %
  IM ............... 4 / 3 %
  Pa+g2(o) ......... 2x38 / 2x28.5 W
  Pa+g2(max sig) ... 2x17 / 2x16 W
  V(g1-g1)(ac) crest 104 / 71 V
  Zout ............. 4.8 / 4.5 kΩ

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Push-Pull. Class AB1. Fixed Bias. Ultra-Linear Connection (40% Tapping Points):   (col1 / col2)
  Va,g2(b) ......... 560 / 460 V
  Va,g2(o) ......... 553 / 453 V
  Ia+g2(o) ......... 2x50 / 2x50 mA
  Ia+g2(max sig) ... 2x157 / 2x140 mA
  RL(a-a) .......... 4.5 / 4 kΩ
  -Vg1 (approx) .... 75 / 59 V
  Pout ............. 100 / 70 W
  Dtot ............. 2 / 2 %
  IM ............... 11 / 10 %
  Pa+g2(o) ......... 2x27.5 / 2x22.5 W
  Pa+g2(max sig) ... 2x33 / 2x27 W
  V(g1-g1)(ac) crest 140 / 114 V
  Zout ............. 7 / 6.5 kΩ
Push-Pull. Class AB1. Cathode Bias. Triode Connection:   (col1 / col2)
  Va,g2(b) ......... 400 / 485 V
  Va,g2(o) ......... 349 / 422 V
  Ia+g2(o) ......... 2x76 / 2x94 mA
  Ia+g2(max sig) ... 2x80 / 2x101 mA
  RL(a-a) .......... 4 / 4 kΩ
  -Vg1 (approx) .... 40 / 50 V
  Pout ............. 17 / 31 W
  Dtot ............. 1.5 / 1.5 %
  IM ............... 5.6 / 5.6 %
  Pa+g2(o) ......... 2x26.5 / 2x40 W
  Pa+g2(max sig) ... 2x19 / 2x27 W
  Rk ............... 2x525 / 2x525 Ω
  V(g1-g1)(ac) crest 78 / 114 V
  Zout ............. 2 / 1.9 kΩ

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INSTALLATION: Tube may be mounted vertically or horizontally. Socket centres not less than 4in apart; pins 4 and 8 of each tube in line (vertical) or same vertical line (horizontal). One tube not directly above another. Free air circulation desirable.
OUTLINE:
  Base: Metal shell wafer octal
  Max overall length: 125 mm; 110 (seated); 52 dia. (mm, maximum)
Pinout:
  Pin 1 = base shell
  Pin 2 = h (heater)
  Pin 3 = a (anode)
  Pin 4 = g2 (screen)
  Pin 5 = g1 (control grid)
  Pin 6 = NP (no pin)
  Pin 7 = h (heater)
  Pin 8 = k, bp (cathode + beam plates)

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[courbes seules — Ia(mA) vs Va(V): Vg2=100V (Vg1=0 à -16V) et Vg2=150V (Vg1=0 à -24V), avec Ig2(Vg1=0)]

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[courbes seules — Ia(mA) vs Va(V): Vg2=200V (Vg1=0 à -28V) et Vg2=300V (Vg1=0 à -45V), avec Ig2(Vg1=0)]

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[courbes seules — TRIODE CONNECTION: Ia vs Va, Vg1=0 à -80V. + ULTRA-LINEAR 40% TAPS: Ia vs Va/Vg2, Va,g2(o)=425V, Vg1=0 à -60V]