Ampera
TT21
Tetrode · IHT · Octal + Top Cap · 1957
“KT88 with top cap. Transmitter heritage.”
Beam power tetrode rated at 37.5W for high-power output stages
TRANSCONDUCTANCE0mA/V
Cgk0pF
Cgp0pF
Cpk0pF
GAIN0%
POWER94%
DRIVE50%
LINEARITY75%
EXECUTIVE SUMMARY
The TT21 is a indirectly-heated beam tetrode from GEC·MOV, introduced around 1957. Commonly used in power (pp) applications. KT88 with top cap. Transmitter heritage.
APPLICATIONS
High-power output
Generic tetrode power (pp) stage
• PA/public address
HISTORY
Introduced1957ManufacturerGEC·MOVEquivalentsKT88 (different pinout)
Golden AgeSPECIFICATIONS
Heater Voltage6.3V
Heater Current1.6A
Max Plate Voltage1250V
Max Power37.5W
Sensitivity11.5 mA/V
Gain Factor—
Internal Impedance—
PinoutOctal + Top Cap
Era1957
RarityCollector
Input Capacitance12pF
Miller Capacitance0.5pF
Output Capacitance8pF
SPICE model not yet available. Loadline calculator requires calibrated Koren parameters.