AR 600A400, Operating And Service Manual

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Rev A 25
3. THEORY OF OPERATION
3.1 INTRODUCTION
The Model 600A400 RF amplifier consists of a .01-400 MHz RF amplifier assembly. The RF amplifier
assembly consists of a Pre-Amplifier (Pre-Amp), one driver amplifier module, and eight final amplifier
modules.
The power supply section consists of an AC input line filter circuit breaker, +5V, -15V, +24V, two +40V
power supplies, an Operate/Control circuit, and an interface board.
The control system consists of a Control/Fault Board, an Interface Board and remote interfaces for IEEE-488,
RS-232, USB, and Ethernet.
3.2 RF AMPLIFIER OPERATION
3.2.1 A1 Pre-Amplifier Assembly (Schematic No. 10045472,
10041352, 10045475)
The Pre-Amplifier Assembly consists of 3 sub-assemblies: the A1 Pre-Amplifier Assembly, the A2 Switch
Assembly, and the A3 Output Amplifier Assembly.
3.2.1.1 A1 Pre-Amplifier Assembly (Schematic 10045472)
The Pre-Amplifier PWB Assembly consists of a variable attenuator circuit (Q1-Q4), a gain stage (U4), a
resistive splitter (R13, R14, R16), an RF power detector (U6), and associated control circuitry. The overall
gain of the pre-amplifier assembly is approximately 6-8 dB at minimum attenuation. The power detector (U6)
is used to sense the input RF power and it increases the attenuation of the variable attenuator circuit if an
input overdrive condition is detected.
3.2.1.2 A2 Switch Assembly (Schematic 10041352)
The Switch Assembly is made up of a variable attenuator circuit (Q1-Q4) and associated control circuitry.
The switch can either be in an on or off state depending on the Inhibit input signal (E4). In the off state, when
E4 is pulled low, the switch will reduce the amplifier gain by approximately 40 dB.
3.2.1.3 A3 Output Amplifier Assembly (Schematic 10045475)
The Output Amplifier Assembly has a single gain stage (U1 ) that has a gain of approximately 15 dB.