KT88SBeamTetrode

The KT88S has an absolute maximum anode dissipation rating of 50W and is designed for use in
the output stage of an a.f. amplifier. Two tubes in Class AB1 give a continuous output of up to 120W.
The KT88 is also suitable for use as a series tube in a stabilised power supply.
HEATER
Vh ................................................................................................................................................................................. 6.3
Ih (approx.) .......................................................................................... 1.6

VAMAXIMUM RATINGS
Absolute and Design Maximum
V ..................................................................................................................................................................... 800
Vg2 ................................................................................................................................................................... 600
Va,g2 ................................................................................................................................................................ 600-Vg1 ................................................................................................................................................................. 200pa ...................................................................................................................................................................... 50
pg2 .................................................................................................................................................................... 8pa+g2 ................................................................................................................................................................ 59Ik ........................................................................................................................................................................ 230
Vh-k .................................................................................................................................................................. 250
Tbulb ................................................................................................................................................................. 250
Rg1-k (cathode bias)
pa+g2 <40W .................................................................................. 470
pa+g2 >40W .................................................................................. 270
Rg1-k (fixed bias)
pa+g2 <40W .................................................................................. 220
pa+g2 >40W .................................................................................. 100aVVV
V
W
W
W
mA
VoCkΩkΩkΩkΩ(Revised 3/1/96)

P E N T A

L A B O R A T O R I E S

9740 COZYCROFT AV. * CHATSWORTH * CALIFORNIA 91311(800) 421-4219 * (818) 882-3872 * FAX: (818) 882-3968

ELECTRON TUBES FOR INDUSTRY

-KT88S

BEAM TETRODE

CAPACITANCES (measured on a cold unscreened tube)
Triode Connection
Cg1-a,g2 ...................................................................................................................................................................... 7.9
Cg1-all less a,g2 .......................................................................................................................................................... 9.3
Ca,g2-all less g1 .......................................................................................................................................................... 17

pF
pF
pF

Tetrode Connection
Cg1-a ........................................................................................................................................................................... 1.2
Cg1-all less a ............................................................................................................................................................... 16
Ca-all less g1 ............................................................................................................................................................... 12

pF
pF
pF

CHARACTERISTICS
Triode Connection
Va,g2 ............................................................................................................................................................................ 250
Ia+g2 .............................................................................................................................................................................. 143-Vg1 (approx.) ............................................................................................................................................................. 15
gm ................................................................................................................................................................................ 12ra ................................................................................................................................................................................... 670µ .................................................................................................................... 8VmAVmmhoΩ

Tetrode Connection
Va ................................................................................................................................................................................. 250
Vg2 ............................................................................................................................................................................... 250
Ia .................................................................................................................................................................................... 140
Ig2 (approx.) .................................................................................................................................................................. 3-Vg1 (approx.) ............................................................................................................................................................. 15
gm ................................................................................................................................................................................ 11.5
ra ................................................................................................................................................................................... 12µg1-g2 ........................................................................................................................................................................... 8

VVmAmA
VmmhokΩ

TYPICAL OPERATION
Push-Pull. Class Ab1, Cathode Bias, Tetrode Connection
Va(b) ............................................................................................................................................................................. 560
Va(o) ............................................................................................................................................................................. 521
Vg2 ............................................................................................................................................................................... 300
Ia(o) ................................................................................................................................................................................ 2 x 64
Ia (max signal) ............................................................................................................................................................... 2 x 73
Ig2(o) .............................................................................................................................................................................. 2 x 1.7
Ig2 (max signal) ............................................................................................................................................................. 2 x 9
RL(a-a) .......................................................................................................................................................................... 9*Rk ............................................................................................................................................................................... 2 x 460-Vg1 (approx.) .............................................................................................................................................................. 30
Pout .............................................................................................................................................................................. 50Dtot .............................................................................................................................................................................. 3Page 2VVVmAmAmAmAkΩΩ
VW%KT88S

BEAM TETRODE**I.M. .................................................................................................. 11pa(o) ............................................................................................................................................................................. 2 x 33pa (max signal) ............................................................................................................................................................. 2 x 12
pg2 (o) .......................................................................................................................................................................... 2 x 0.5
pg2 (max signal) ........................................................................................................................................................... 2 x 2.7
V(g1-g1)(ac) crest ........................................................................................................................................................ 60%
WW
W
W
V

* It is essential to use two seperate cathode bias resistors.
** Intermodulation distortion; measured using two input signals at 50 and 6000 Hz (ratio ofplitude 4:1)

am-Push-Pull. Class AB1, Fixed Bias, Tetrode Connection
Va(b) ............................................................................................................................................................................. 560
Va(o) ............................................................................................................................................................................. 552
Vg2 ............................................................................................................................................................................... 300
Ia(o) ................................................................................................................................................................................ 2 x 60
Ia (max signal) ............................................................................................................................................................... 2 x 145
Ig2(o) .............................................................................................................................................................................. 2 x 1.7
Ig2 (max signal) ............................................................................................................................................................. 2 x 15
RL(a-a) .......................................................................................................................................................................... 4.5*-Vg1 (approx.) ............................................................................................................................................................. 34
Pout .............................................................................................................................................................................. 100
Dtot .............................................................................................................................................................................. 2.5**I.M. .................................................................................................. 10pa(o) ............................................................................................................................................................................. 2 x 33
pa (max signal) ............................................................................................................................................................. 2 x 28
pg2 (o) .......................................................................................................................................................................... 2 x 0.5
pg2 (max signal) ........................................................................................................................................................... 2 x 4.5
V(g1-g1)(ac) crest ........................................................................................................................................................ 67

VVVmA
mAmAmAkΩVW%%WWWWV* It is essential to provide two seperately adjustable bias bias voltage sources, having aage adjustment range of +/- 25%** Intermodulation distortion; measured using two input signals at 50 and 6000 Hz (ratio ofplitude 4:1)
Push-Pull. Class AB1, Cathode Bias, Ultra-Linear Connection (40% Tapping Points)
Va,g2(b) ................................................................................................................................... 500
Va,g2(o) ................................................................................................................................... 436
Ia+g2(o) ..................................................................................................................................... 2 x 87
Ia+g2(max signal) ...................................................................................................................... 2 x 99
RL (a-a) ................................................................................................................................... 6*Rk .......................................................................................................................................... 2 x 600-Vg1 (approx.) ......................................................................................................................... 52

Page 3375328
2 x 872 x 965
2 x 400
35

VVmAmAkΩΩ
Vvoltam-KT88S

BEAM TETRODE

Pout ......................................................................................................................................... 50Dtot ......................................................................................................................................... 1.5**I.M. ............................................................................ 4pa+g2(o) ................................................................................................................................... 2 x 38
pa+g2(max signal) ................................................................................................................... 2 x 17
V(g1-g1)(ac)crest .................................................................................................................... 104
Zout .......................................................................................................................................... 4.830
132 x 28.5
2 x 16
71
4.5

W%%
W
WVkΩ

* It is essential to use two seperate cathode bias resistors.
** Intermodulation distortion; measured using two input signals at 50 and 6000 Hz (ratio ofplitudes 4:1)am-Push-Pull. Class AB1, Fixed Bias, Ultra-Linear Connection (40% Tapping Points)
Va,g2(b) ................................................................................................................................... 560
Va,g2(o) ................................................................................................................................... 553
Ia+g2(o) ..................................................................................................................................... 2 x 50
Ia+g2(max signal) ...................................................................................................................... 2 x 157
RL (a-a) ................................................................................................................................... 4.5*-Vg1 (approx.) ...................................................................................................................... 75
Pout ......................................................................................................................................... 100
Dtot ......................................................................................................................................... 2**I.M. ............................................................................ 11pa+g2(o) ................................................................................................................................... 2 x 27.5
pa+g2(max signal) ................................................................................................................... 2 x 33
V(g1-g1)(ac)crest .................................................................................................................... 140
Zout .......................................................................................................................................... 7460453
2 x 502 x 140
45970
2102 x 22.5
2 x 27
114
6.5

VVmAmAkΩVW%%
WWVkΩ* It is essential to provide two seperately adjustable bias bias voltage sources, having aage adjustment range of +/- 25%** Intermodulation distortion; measured using two input signals at 50 and 6000 Hz (ratio ofplitude 4:1)
Push-Pull. Class AB1, Cathode Bias, Triode Connection
Va,g2(b) ................................................................................................................................... 400
Va,g2(o) ................................................................................................................................... 349
Ia+g2(o) ..................................................................................................................................... 2 x 76
Ia+g2(max signal) ...................................................................................................................... 2 x 80
RL (a-a) ................................................................................................................................... 4-Vg1 (approx.) ......................................................................................................................... 40Pout ......................................................................................................................................... 17Dtot ......................................................................................................................................... 1.5*I.M. ............................................................................. 5.6pa+g2(o) ................................................................................................................................... 2 x 26.5pa+g2(max signal) ................................................................................................................... 2 x 19
Page 4485422
2 x 942 x 101
45031
1.5
5.6
2 x 402 x 27

VVmAmAkΩ
VW%%
W
W

voltam-KT88S

BEAM TETRODE

Rk ............................................................................................................................................ 2 x 525
V(g1-g1)(ac)crest .................................................................................................................... 78
Zout .......................................................................................................................................... 2

2 x 525
114
1.9Ohms
VkΩ* Intermodulation distortion; measured using two input signals at 50 and 6000 Hz (ratio ofplitude 4:1)

am-INSTALLATION
The tube may be mounted either vertically or horizontally.
When the tubes are mounted vertically, it is recommended that the centers of the tube sockets are
not less than 4 inches apart and that pins 4 and 8 of each tube are in line.
When the tubes are mounted horizintally, it is recommended that the centers of the tube sockets
are not less than 4 inches apart and that pins 4 and 8 of each tube are in the same vertical line.
One tube should not be mounted directly above another.
Free air circulation around the tube is desirable.

Base: Metal shell, wafer octal
Pin:
1. N.C.
2. h
3. a
4. g2
5. g1
6. N.C.
7. h
8. k,bp

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