NV5/NV3.5 Troubleshooting Manual Detailed Circuit Descriptions
Page 2-4 Issue 3.2 2014-12-10
The RF Drive input is applied to cable T1, which is connected as a balun to provide balanced, 180°
out-of-phase, RF drive signals to the individual gates of dual N-channel power MOSFET (Q1).
Cables T2:A and T2:B, as well as capacitors C2, C6, C7 and C17, inductor L2 (part of R12/R13 leads)
and resistors R5, R8 through R10, R12 and R13 provide impedance matching, which transforms the
50 ohm input to low impedance for application to Q1. The PA voltage is applied to the individual
drains of Q1 via inductors L4 and L5, which provide proper resonating reactance for Q1's output.
Cable T3:A and T3:B transform the impedance at the RF output, ensuring an optimum (low)
impedance is presented at Q1's output. Cable T4 converts the balanced RF signal to an unbalanced
RF Output signal.
The PA V input is applied to capacitors C1, C3, C5, C8 and C11, which act as a broadband
decoupling network. Capacitor C13 and inductor L3 provide low-pass filtering of the RF signal back
to the ac-dc power stage.
The Bias input voltage is provided by the power module interface PWB to establish a dc bias current
for Q1. The bias current depends on the operating mode and whether the amplifier is in an RF power
module or an IPA module.
Power module interface PWB
See Figures SD-25 through SD-27. The power module interface PWB (A10) monitors and distributes
the RF drive and the dc supply current to the individual power amplifiers of the IPA or RF power
module. Its main functions are:
• Monitoring the current supplied to each PA and cause an alarm condition if a PA stops
drawing current.
• Providing a low level dc signal, proportional to the intermediate RF drive power, for
monitoring.
• Providing each PA's dc bias voltage.
• Inhibiting the associated switching power supply module when the appropriate fault occurs.
• Communicating with the control/monitor stage on module specific status and alarm
parameters.
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