User Manual

Unit 5 – 250W Amplifier
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1. 250W Amplifier:
1.1. Introduction:
This module amplifies the RF power that comes from 1:4 divisor to 250W, then they are
combined to obtain the 1000W RF power, maintaining its characteristics and the same bandwidth.
1.2. Protections and Monitoring:
For these functions, we have:
VSWR Circuit: it protects the amplifier module transistors, when the output stationary wave is
superior to 4%. This circuit acts in the output transistors gates.
Temperature Circuit: it acts in the output transistors gate when the heat sink temperature is above
56°C.
Forward power circuit: it acts in the output transistors gates when the RF output power exceeds the
pre-fixed value, this way limiting the maximum RF power.
1.3. Power supply input:
The protection fuses are in this circuit.
This circuit supplies the informations about the amplifier currents.
1.5. Amplifier stages:
Two 125W amplifier modules are used in parallel. This module uses 4 transistors MRF 373
A. Its
gain is approximately 18 dB in AB class.