5-5.2 High-Power Board
See Figure 5-12. The High-Power board comprises the Power Amplifier and the Harmonic Filter
circuits.
Pre-Driver
Amplifier
ALC
Circuit
-6 to -3 dBm
(for full power)
Figure 5-12. High Power Board Functional Block Diagram
5-5.2.1 Power Amplifier (PA)
The PA contains three RF (1.6 to 30 MHz) wide band amplification stages:
• Pre-driver (Q2, Q6)
• Push-pull driver (Q32, Q33)
• Final push-pull power stage (Q35, Q34).
The PA also includes a control circuit which controls the output power level according to the control
signal provided by the ALC D/A (controlled by the microprocessor on the LORD board) and the
temperature at the final push-pull transistor case. This circuit is implemented by three operational
amplifiers (U6) that receive inputs from the ALC D/A and the VSWR detector (the harmonic filter
circuit). It controls an active attenuator (CR54 and CR56), which regulates the RF input to the
amplification stages.
5-14 Cat. No. 6886859J01
To Next Page
Loading...
