Agilent Technologies 33120A manual

Chapter 5 Theory of Operation

Waveform DAC/Amplitude Leveling/Waveform RAM

Waveform DAC/Amplitude Leveling/Waveform RAM

Block 4 on block diagram page 129; Schematic on page 134.

The Waveform DAC, U407, converts 12-bit digital data from waveform RAM’s U404 and U405 into positive and negative analog voltages.

A simplified diagram of the Waveform DAC circuitry is shown below.

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The preattenuator, filters, and associated circuits in the output signal path provide an approximate 25W load for the Waveform DAC. The Waveform DAC nominally produces a 40 mA differential output current — yielding differential 1 Vac output signals. Wave shape (amplitude) data is loaded into the waveform RAM by the main controller CPU U102. Once loaded, these data are addressed by the DDS ASIC. The rate at which addresses are incremented determines the output waveform frequency. Waveform RAM output data is latched and shifted to ECL levels by U402 and U403 for input to the waveform digital-to-analog converter (DAC) U407. DDS ASIC U206, waveform data latches U402 and U403, and the Waveform DAC U407 are clocked at 40 MHz. The 40 MHz clock is generated by oscillator U413 and ECL level-shifter U401.

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Agilent Technologies 33120A Waveform DAC/Amplitude Leveling/Waveform RAM, Block 4 on block diagram page 129 Schematic on

Contents

Agilent 33120A MHz Function Arbitrary Waveform Generator Service GuidePage Flexible system features Convenient bench-top features Front Panel at a Glance Front-Panel Number Entry MODulation Menu Front-Panel Menu at a Glance Trig Display Annunciators Use the front-panel Input / Output Menu to Rear Panel at a Glance This Book Page Contents Contents Replaceable Parts ServiceSchematics Contents Specifications Waveforms Modulation Characteristics General Specifications Product Dimensions Page Quick Start Quick Start Check the list of supplied items One User’s Guide 〈 This Service GuideConnect the power cord and turn on the function generator To prepare the function generator for use If the function generator does not turn on Verify that there is ac power to the function generatorVerify the power-line voltage setting Verify that the power-line fuse is good Remove the power cord . Remove To adjust the carrying handle Set the units to the desired value To cancel the number mode, press Shift CancelTo set the output frequency Enter the magnitude of the desired frequency Enter the magnitude of the desired amplitude To set the output amplitude Enter the magnitude of the desired offset How to change the offset to -1.5 mVdcEnable the offset modify mode To set a dc offset voltage Output the waveform with the displayed duty cycle To set the duty cycleSelect the square wave function Enter the desired duty cycle Select and output the displayed arbitrary waveform To output a stored arbitrary waveformDisplay the list of arbitrary waveforms Move across to the Exprise choice Enter the magnitude of the desired voltage To output a dc voltage Save the instrument state Set up the function generator to the desired configurationTurn on the state storage mode To store the instrument state Recall the stored instrument state Restore the instrument state To rack mount the function generator Quick Start Front-Panel Menu Operation Front-Panel Menu Operation MODulation Menu Front-panel menu reference Front-panel menu reference SYStem Menu Front-panel menu tutorial Messages Displayed During Menu Use Move across to the SYS Menu choice on this level Move across to the Power on command on this levelTurn on the menu Save the change and turn off the menu Cycle the power to restore the default valuesMove down a level to the Parameter choices Increment the first digit until 300.0 mVPP is displayed Select amplitude adjustment Move down a level and then across to the High Z choice Move down a level to the OUT Term commandTo select the output termination Use the menu to select the shape of the modulating waveform To output a modulated waveformSelect AM Set the modulation depth to 80% Move down a level verify that Sine is selectedSet the modulating frequency to 200 Hz Move across to the CAL Menu choice on this level Move down a level to the Secured commandTo unsecure the function generator for calibration Move down to the parameters level Calibration Procedures Calibration Procedures Time Required for Calibration Agilent Calibration ServicesCalibration Interval Recommended Test Equipment Automating Calibration Procedures Test Considerations Self-Test Performance Verification Tests Quick Performance Check Function Gain and Linearity Verification Frequency Verification AC Amplitude Verification DC Function Offset Verification AC Amplitude Verification Vrms 0.00035 Vrms 15.00 MHz Amplitude Flatness Verification Vrms 0.0061 Vrms AM Modulation Depth Verification Square Wave Duty Cycle Verification Optional Performance Verification Tests Distortion Verification Characters Calibration Security Code To Unsecure the Function Generator Without the Security Code Calibration Message Calibration Count Move across to the Calibrate choice General Calibration/Adjustment ProcedureMove down a level to the Unsecured command Begin the Frequency and Burst Rate adjustment procedure Calculate and save the new value Perform the next adjustment procedure Aborting a Calibration in Progress Frequency and Burst Rate Adjustment AC Amplitude Adjustment High-Z Function Gain and Linearity Adjustment AC Amplitude Adjustment High-Z Frequency Amplitude Modulation Adjustment AC Amplitude Adjustment 50W AC Amplitude Adjustment 50W Adjustment for KHz Setup DC Output Adjustment AC Amplitude Flatness Adjustment Duty Cycle Adjustment AC Amplitude Flatness Adjustment Exiting Output Amplifier Adjustment Optional Self-Test Error Messages Error MessagesSystem Error Messages Calibration Error Messages Theory of Operation Theory of Operation Self-test procedures are described in chapter This discussion pertains to the block diagram shown on Block Diagram Overview Output Attenuator Block 8 on block diagram page 129 Schematic on Output Amplifier Block 7 on block diagram page 129 Schematic on 740 R710 R717 740 R710 R711 R715 R716 R719 R720 AM Modulation Square Wave and Sync Block 6 on block diagram page 129 Schematic onBlock 6 on block diagram page 129, schematic on Pre-attenuator Square Wave and Sync Filters Block 5 on block diagram page 129 Schematic on Waveform DAC/Amplitude Leveling/Waveform RAM Block 4 on block diagram page 129 Schematic on Waveform DAC/Amplitude Leveling/Waveform RAM Direct Digital Synthesis DDS Asic Block 2 on block diagram page 129 Schematic on System DACs Block 3 on block diagram page 129 Schematic on Floating Logic Block 1 on block diagram page 129 Schematic on Earth-Referenced Logic Power SuppliesBlock 9 on block diagram page 129 Schematic on Block 10 on block diagram page 129 Schematic on Power Supplies See Block 11 on block diagram page 129 Schematic onDisplay and Keyboard Service Service Does the function generator fail self-test? Operating ChecklistIs the function generator inoperative? See To prepare the function generator for use on Call 1-877-447-7278 and ask for Agilent Express Types of Service Available Agilent suggests that you always insure shipments CleaningRepackaging for Shipment Surface Mount Repair Electrostatic Discharge ESD Precautions To Replace the Output Protection Fuse F801 To Replace the Power-Line Fuse Unit Fails Self-Test Troubleshooting HintsUnit Reports Error Unit is Inoperative Power Supply Problems Power-On Self-Test Self-Test Procedures 625 112 Replaceable Parts Replaceable Parts Main PC Assembly 116 117 118 119 120 121 122 123 Display and Keyboard PC Assembly 33120A Mainframe Manufacturer’s List Schematics8 Schematics Block Diagram Pull Off Handle Loosen Captive Sheet 1 132 Sheet 3 Sheet 4 Waveform DAC Schematic 134 Sheet 5 136 Sheet 7 Sheet 8 Output Attenuator Schematic 138 Sheet 9 of 10 Earth Reference Logic Schematic Sheet 10 Power Supplies Schematic 140 Sheet 1 of 1 Display and Keyboard Schematic TOP Side 33120-66521 REV a TOP Side 33120-66502 REV C Manual Part Number