Agilent Technologies 33120A manual Block Diagram Overview

Chapter 5 Theory of Operation

Block Diagram Overview

Block Diagram Overview

This discussion pertains to the block diagram shown on page 129.

The function function generator’s circuitry is divided into two major blocks: the floating section and the earth (ground) reference section. All signal generation, control, and display functions are contained in the floating section. This section also contains the function generator’s main CPU.

The floating section can be viewed in two pieces; the analog signal conditioning section (System DAC, Filters, Sync, Square wave, Pre-Attenuator, Output Amp, and Output Attenuator) and the digital logic section (Floating Logic, Digital Waveform Data Synthesis, and Waveform DAC).

All signal generation, level control, and modulation functions are performed in the floating section. The waveform DAC generates two outputs, normal and inverted, between approximately 800 mVp-p and

1Vp-p. The DAC outputs are routed through anti-alias low-pass filters to eliminate higher frequency sampling products. The nominal x10 gain of the output amplifier, combined with preattenuator and output attenuator settings, are chosen such that the desired output amplitude is produced.

The ground reference section uses a processor configured as a slave to the 5 main CPU. This processor establishes external I/O communication with

the main CPU through a bi-directional, optically isolated, serial communications link. The earth referenced processor controls low-level GPIB (IEEE-488) and RS-232 interface operation. The ground referenced, rear panel external trigger input uses a dedicated optical isolator to couple a trigger signal to the main CPU in the floating section.

Separate power supplies are provided for the floating and ground reference sections. The front panel operates from the floating section with its logic common different from the CPU logic common.

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