User's Manual

Ma in t ena n ce Bulle t in Topic: Fla n ged RF Am plifier Tr ansist or s
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St ep 1. Caut ion: I f the device being replaced is a GaAs FET, before applying the Posit ive
Volt age t o t he Device check t hat t he Negat ive Bias Volt age is applied t o the Device.
9. The am ount of St atic Collector or Drain Current is calculat ed using Ohm 's Law ( I = E\ R).
Measure t he volt age drop across t he Collector or Drain Resist or, one lead on each side of the
Resist or. I n am plifiers using Bipolar Transistors, t he Resist or is locat ed on the Am plifier Board
in the Collector Circuit of the Transist or near where the Supply Voltage ent ers the Board. I n
am plifiers that have GaAs FETs the Resistor is locat ed on the GaAs FET Cont rol Board or on
the Am plifier Board in the Drain Circuit . Adj ust t he Bias Adj ustm ent Pot locat ed in the Gat e
Circuit until the desired volt age drop is m easured across the .1 ohm resistor. See the Det ailed
Alignm ent Procedure for t he Tray in which the Am plifier Board is locat ed t o find the am ount of
Collector or Drain Current and the necessary Voltage Drop needed to at t ain it .
N ote : See t he Det ailed Alignm ent Procedure for t he Tray in w hich t he am plifier board is
located to find t he am ount of collector or drain current and the necessary voltage
drop needed to at t ain it .
10. Reapply t he RF Drive t o the Module and you are ready for norm al operat ion.