GU78B
TETRODE
The GU78B tetrode is used for power amplification in distributed amplifiers and singlesideband signal amplifiers at frequencies up to 250 MHz, in RF industrial engineering equipment.
GENERAL
Cathode: indirectly heated, oxidecoated.
Envelope: metal ceramic, with ring leads of cathode, grid 2 and anode and pin leads of grid 1.
Cooling: forced air.
Height: at most 120 mm.
Diameter: at most 111 mm.
Mass: at most 1.8 kg.
OPERATING ENVIRONMENTAL CONDITIONS  
Vibration loads:  
frequencies, Hz  160 
acceleration, m/s²  20 
Multiple impacts with acceleration, m/s²  150 
Ambient temperature, °C  60 to +70 
Relative humidity at up to +25 °C without moisture condensation, %  98 
BASIC DATA Electrical Parameters 

Heater voltage (AC or DC), V  27 
Heater current, A  3.44 
Anode voltage, kV  1.7 
Grid 2 voltage, V  300 
Negative grid 1 bias voltage, V  5125 
Negative cutoff voltage (at anode voltage 3 kV, anode current 20 mA), absolute value, V 
150 
Anode current, A  1.5 
Anode current at zero grid 1 voltage (at anode voltage 250 V), mA, at most  4.2 
Grid 2 current at zero grid 1 voltage (at anode voltage 250 V), mA, at most  0.9 
Mutual conductance, mA/V  4080 
Output power under amplification of class AB_{1}, kW:  
at heater voltage 27 V, at least  2.5 
at heater voltage 25.7 V, at least  2.2 
Commoncathode interelectrode capacitance, pF:  
input  100150 
output  1530 
transfer, at most  0.25 
Limit Operating Values  
Heater voltage (AC or DC), V  25.528.3 
Anode voltage, V:  
DC  3,200 
instantaneous value  6,200 
Grid 2 voltage (DC), V  350 
Negative grid 1 voltage (DC, absolute value), V  150 
Cathodeheater voltage (either polarity, absolute value), V  150 
Cathode current (DC component), mA  2,200 
Grid 1 current (DC component), mA  25 
Dissipation, W:  
anode  2,500 
grid 2  30 
grid 1  1 
Operating frequency, MHz  250 
Cathode heating time, s  240 
Envelope temperature at hottest point, °C  200 
Averaged Anode Characteristic Curves:
U_{f} = 27V; U_{g2} = 300V
Averaged Characteristic Curves:
U_{f} = 27V; U_{g2} = 300V;
_____ anode grid;
_ _ _ grid 2;
_ . _ grid 1
Averaged GridAnode Characteristic Curves:
U_{f} = 27V; U_{g2} = 300V;
————— I_{g2}
   I_{g1}