Operator’s Manual DA1855A Differential Amplifier
DA1855A Differential Amplifier Operator’s Manual February 2013
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Operator’s Manual Table of Contents Safety Instructions ................................................................................................................... 1 Symbols .............................................................................................................................. 1 Precautions ......................................................................................................................... 1 Operating Environment ..........................................
DA1855A Differential Amplifier Introduction ....................................................................................................................... 39 Voltage Measurements ..................................................................................................... 39 Measuring Current ............................................................................................................ 39 Effects of Probes on Saturation Voltage Measurements ....................................
Operator’s Manual Safety Instructions This section contains instructions that must be observed to keep this oscilloscope accessory operating in a correct and safe condition. You are required to follow generally accepted safety procedures in addition to the precautions specified in this section. The overall safety of any system incorporating this accessory is the responsibility of the assembler of the system.
DA1855A Differential Amplifier Use indoors only. Keep product surfaces clean and dry. Do not block the cooling vents. Leave a minimum six-inch (15 cm) gap between the instrument and the nearest object. Keep the underside clear of papers and other objects. Do not remove the covers or inside parts. Refer all maintenance to qualified service personnel. Do not operate with suspected failures. Do not use the product if any part is damaged.
Operator’s Manual Calibration The amplifier is calibrated at the factory prior to being shipped. The recommended calibration interval is one year. Calibration should be performed by qualified personnel only. Schedule an annual factory calibration as part of your regular maintenance. Extended warranty, calibration, and upgrade plans are available for purchase. Contact your Teledyne LeCroy sales representative or customersupport@teledynelecroy.com to purchase a service plan.
DA1855A Differential Amplifier Specifications These specifications are valid for instruments when the following conditions have been met: • The instrument is being operated from a power source, which meets the line voltage and frequency specifications. • The instrument has been operating for at least 20 minutes in an environment, which is within the operating environmental specifications. • The instrument has been calibrated within the last 12 months.
Operator’s Manual General, continued Auto Zero Effective Gain Indicator Amplifier initiates an automatic balance cycle, when either gain button is depressed, to remove output offset drift Indicators show the effective system gain or attenuation, factoring Probe Attenuation, Attenuator and gain settings. (Probe must have coding connectors. ÷1, ÷10, ÷100 and ÷1000 probes are recognized) Dynamic Ranges Maximum Differential Mode Range X10 Gain, ÷1 Attenuator ± 50 mV1 X1 Gain, ÷1 Attenuator ± 0.
DA1855A Differential Amplifier Precision Voltage Generator Output Range ± 15.
Operator’s Manual Typical Characteristics Typical characteristics describe parameters, which do not have guaranteed performance. Tests for typical characteristics are not provided in the Performance Verification Procedure. Input Resistance ÷1 Attenuator 1 MΩ or 100 MΩ 1 MΩ only when used with attenuating probe ÷10 Attenuator 1 MΩ Input Capacitance 20 pF AC Input Coupling Capacitance 0.1 μF ÷10 Attenuator Accuracy 0.
DA1855A Differential Amplifier Physical Characteristics Height Width Depth Weight Shipping Weight 8 DA1855A 7.29 cm (2.87 inch) DA1855A-PR2 8.75 cm (3.4 inch) DA1855A 21.2 cm (8.36 inch) DA1855A-PR2 43.9 cm (17.3 inch) DA1855A 23.2 cm (9.12 inch) DA1855A-PR2 42.5 cm (16.7 inch) DA1855A 2.15 kg (4 lbs 12 oz.) DA1855A-PR2 9.5 kg (21 lbs) DA1855A 3.12 kg (6 lbs 14 oz.) DA1855A-PR2 11.
Operator’s Manual Overview The DA1855A is a stand-alone high performance 100 MHz differential amplifier. It is intended to act as signal conditioning preamplifier for oscilloscopes, spectrum analyzers and other instruments, providing differential measurement capability to instruments having only a single-ended input. When used with a DA1855A, high quality oscilloscopes can obtain common mode rejection and overdrive recovery performance that was previously unobtainable in any product.
DA1855A Differential Amplifier Model Description The DA1855A series is comprised of 2 models which differ in physical configuration. Both contain the same 100 MHz differential amplifier which provides high common mode rejection, extremely fast overdrive recovery, selectable ÷1 or ÷10 attenuation, selectable X1 or X10 gain, a 5-1/2 digit Precision Voltage Generator (PVG), selectable upper bandwidth limiting filters, and effective gain display. and ± 500 mV output swing limiting.
Operator’s Manual Optional Accessories • Service Manual, containing adjustments, repair and replacement part information P/N: DA1855A-SM-E. • DXC100A, ÷10 / ÷100 Passive Differential Probe. • DXC200, ÷1 Passive Differential Probe. • DXC5100, ÷100 2.5 K Passive Differential Probe Pair • DA101, External ÷10 Attenuator. Operation General Information The DA1855A has been designed to be used with oscilloscopes equipped with a ProBus interface.
DA1855A Differential Amplifier Front Panel Input Connectors Signals applied to the +INPUT and the –INPUT are connected either directly to the DA1855A amplifier’s inputs or to the input attenuators. Maximum input voltage is ±200 Vp A signal connected to the +INPUT will remain its polarity at the output connector. A signal connected to the –INPUT will be inverted in polarity. Attenuators The input attenuators are passive networks which divide each signal by ten.
Operator’s Manual Unbalanced source impedances can have an adverse effect on common mode rejection. For example, a differential source with impedances of 1000 and 2000 Ω, each loaded with 1 MΩ will have a common mode rejection ratio (CMRR) of 1000 to 1. The common mode rejection ratio can be improved to 100,000 to 1 by using 100 MΩ input resistance. Auto Zero Auto Zero is a feature invoked from the Channel setup dialog when the amplifier is connected via the ProBus interface.
DA1855A Differential Amplifier –3 dB point is 0.016 Hz. This extremely low frequency cut off is useful for observing low frequency noise riding on larger DC voltages. In the DC mode, the +INPUT connector is connected to the amplifier either directly or through the input attenuator, and the AC and DC attenuation are the same. - Input Coupling (AC–OFF – DC – VCOMP) The –INPUT has the same coupling modes as the +INPUT plus one additional option, VCOMP (comparison voltage).
Operator’s Manual PVG to null out an input voltage up to ± 155.00 Volt which is ten times larger than the actual PVG voltage. The increase in common mode voltage range also applies when using attenuating probes. When the DA1855A is used with attenuating probes that feature readout, the PVG display is changed to indicate the voltage at the +INPUT probe tip which will bring the amplifier output to zero.
DA1855A Differential Amplifier Differential Offset VDIFF (differential offset voltage) is an instrument mode rather than a type of input coupling. The VDIFF mode allows the PVG to inject a calibrated offset signal into the DA1855A while still using both inputs for full differential operation. This mode can be used as a position control to move the trace on the oscilloscope screen in preference to using the oscilloscope's position or offset control.
Operator’s Manual 50 Ω load. Without the load, the filter's frequency response and transient response are altered. 1 MHz The 1MHz filter is of the same design as the 20 MHz filter, and the same remarks apply. 100 kHz The 100kHz filter is an active filter with a 50 Ω output impedance. Transient and frequency response are independent of the load impedance.
DA1855A Differential Amplifier Precision Voltage Generator Offset Voltage The rear panel OFFSET VOLTAGE BNC (PVG) output connector, is a monitor of the Precision Voltage Generator (PVG). The voltage present on this connector is the same voltage as that applied to the – INPUT when the –INPUT coupling is set to VCOMP or internally to the DA1855A when VDIFF is selected. The OFFSET VOLTAGE output can be used to monitor the PVG with a digital Voltmeter (DVM).
Operator’s Manual Table 2 and Table 3 will help the operator stay within the maximum input voltage limits and understand the relationship between the actual voltage applied and the effective voltage. Effective voltage is always referred to the input of the DA1855A or the probe tip if a probe is used. When using probes, the maximum effective voltage range may be limited by the maximum voltage rating of the probe.
DA1855A Differential Amplifier Remote Operation A REMOTE connector on the rear panel of the DA1855A allows total control of the instrument through a Teledyne LeCroy oscilloscope when connected to ProBus using the supplied cable. All of the instrument functions can be controlled through the oscilloscope user interface. Remote control is also possible using commands sent through the IEEE-488 bus or through RS-232 connected to the oscilloscope.
Operator’s Manual When used without ProBus interface, the instrument can be set to factory default settings by pressing the VCOMP and VDIFF buttons simultaneously. Gain Attenuation X1 ÷10 + Input Coupling Off – Input Coupling Off Bandwidth Limit Full PVG Voltage +00.000 V VCOMP Off VDIFF Off Input Resistance PVG Mode 1 MΩ Roll through zero Table 4.
DA1855A Differential Amplifier More sensitive settings (e.g. 100µV/div) available on some oscilloscopes can be used, but their usefulness may be limited by noise, particularly with the DA1855A FULL bandwidth limit selection and without averaging. With the oscilloscope set to 100µV/div and the DA1855A in the X10 GAIN mode, the overall scale factor will be 10µV/div.
Operator’s Manual compensation procedure can result in a significant decrease in the CMRR capability of any differential probe pair. It is a good practice to compensate a probe pair for a given amplifier and then leave the probe pair and amplifier together as a system. Similarly, it is important that, once compensated for given amplifier, each probe always be used on the same input (one probe always on the +INPUT and the other always on the –INPUT).
DA1855A Differential Amplifier Power Connection Check to make sure the power switch located on the rear panel is in the OFF position. Connect the power cable to an appropriate power source. The DA1855A will operate on a 50 or 60 Hz AC power source with a nominal voltage range from 100 V to 240 V. Comparator Mode The DA1855 becomes a differential comparator when the internal Precision Voltage generator (PVG) output is selected as the amplifier’s inverting (–) input.
Operator’s Manual Figure 2, Block Diagram VDIFF Mode. Setting Up the Oscilloscope with ProBus Interface Connect the RJ-45 type connector of the ProBus interface cable to the REMOTE connector and one end of the BNC cable to the AMPLIFIER OUTPUT on the rear panel of the DA1855A and the other end of the BNC cable to the ProBus connector. Connect the ProBus connector to any vertical channel and, if necessary, press the Front Panel channel button to turn on the channel.
DA1855A Differential Amplifier Make these settings: PVG Mode OFF +Coupling DC –Coupling Grounded (OFF) DA1855A (Atten/Gain) List Select: Upper BWL Auto Full BWL List Select: Gain X1 List Select: Atten ÷10 List Select: Input R 1 MΩ Attenuator and Gain Operation Connect the function generator output to the +INPUT BNC connector and apply a sine wave of 50 kHz and 1.0 Vp-p amplitude. If necessary, set the oscilloscope scale factor to 0.50 V/div.
Operator’s Manual Comparison Voltage Operation (VCOMP) Set the DA1855A as follows: PVG Mode OFF +Coupling DC –Coupling Grounded (OFF) DA1855A (Atten/Gain) List Select: Upper BWL List Select: Gain List Select: Atten List Select: Inpur R 1 Manual FULL BWL X10 ÷1 MΩ Set the Function generator’s output to 50 kHz and 100 mVp-p sine wave and the output connected to the DA1855’s +INPUT. Set the oscilloscope to 5 mV/div.
DA1855A Differential Amplifier the centerline. Following are a few observations on using the DA1855A comparison voltage mode (VCOMP): • The negative input and its AC, OFF and DC coupling are disabled. Instead of being a differential amplifier, the DA1855A becomes a differential comparator. It compares the voltage present at the +INPUT with the output of the Precision Voltage Generator and when they are equal, the output of the DA1855A is zero volts.
Operator’s Manual Set the Function generator’s output to 50 kHz and 100 mVp-p sine wave and the output connected to the DA1855’s +INPUT. Set the oscilloscope to 5 mV/div and time/div adjusted to display 2 to 3 cycles. Externally trigger the oscilloscope by connecting a cable from the function generator’s output (same signal as is applied to the DA1855A's +INPUT) or from the Trigger Signal out on the oscilloscope.
DA1855A Differential Amplifier Following are a few observations on using the differential offset mode (VDIFF) of the DA1855A: • Both the positive and negative inputs (AC, OFF and DC) are enabled and the DA1855A remains a true differential amplifier. • The value displayed by the Precision Voltage Generator indicates a waveform’s differential voltage, with respect to the –INPUT, as it passes through the oscilloscope display’s center line.
Operator’s Manual Attenuator and Gain Operation Connect the function generator output to the +INPUT BNC connector and apply a sine wave of 50 kHz and 1.0 Vp-p amplitude. The signal on the oscilloscope should be 2 divisions peak to peak amplitude. Adjust the oscilloscope’s time per division and trigger to display at least two complete cycles of the waveform.
DA1855A Differential Amplifier Press the –INPUT’s VCOMP button. This internally applies the Precision Voltage Generator’s output to the DA1855A's –INPUT and the OFF light goes out (the –INPUT connector is disabled). The positive and negative peaks of the waveform displayed on the oscilloscope are (respectively) 10 divisions above and below the display center line.
Operator’s Manual • By using the DA1855A in the comparison voltage mode and the oscilloscope in a high sensitivity setting, highly accurate voltage measurements can be made. • The Precision Voltage Generator can be used as a position control which allows the DA1855A to operate in its linear region.
DA1855A Differential Amplifier two places right of the decimal (10mV) in the Precision Voltage Generator until the positive peak of the waveform appears in the oscilloscope’s display. Continue incrementing and decrementing the digits in the Precision Voltage Generator until the peak of the waveform is at the center line of the oscilloscope’s display. The number in the Precision Voltage Generator display is the value of the waveform’s positive peak voltage.
Operator’s Manual • By using the DA1855A in the differential offset mode and the oscilloscope in a high sensitivity setting, high resolution voltage measurements can be made. The –INPUT is the reference for these measurements. • The Precision Voltage Generator can be used as a position control which allows the DA1855A to operate in its most linear region. Determining the Proper Offset Mode The operation of the Comparison (VCOMP ) and Differential Offset modes (VDIFF) are quite similar.
DA1855A Differential Amplifier The maximum common mode range is ± 15.5 Volt when a signal is applied directly (÷1 ATTENUATOR and no probes) to theDA1855A's + and – INPUTs. Attenuating the input signal extends the common mode range by the same factor as the attenuation. Pressing the ÷10 ATTENUATOR button increases the common mode range to±155 Volt, and using a probe with a ÷10 attenuation factor will too.
Operator’s Manual properly set). Thus, a sine wave large enough to overdrive the DA1855A will appear as a square wave on the oscilloscope. The DA1855A is designed to cleanly limit the output signal to± 500 mV. The DA1855A goes into limit when its output reaches ± 500 mV and is designed to recover very quickly once its input signal level decreases sufficiently to allow the amplifier to return to its linear range.
DA1855A Differential Amplifier Care and Maintenance Cleaning Clean only the exterior of the amplifier using a soft cloth moistened with water or isopropyl alcohol. Using abrasive agents, strong detergents or other solvents may damage the exterior of the amplifier. Calibration Interval The recommended calibration interval is one year. Adjustment should only be performed by qualified personnel. A Performance Verification procedure is included in this manual.
Operator’s Manual Applications Introduction Some parts of a power supply operation, such as saturation voltage, upper gate drive, loop response etc., have been difficult to perform without the proper accessories to expand the measurement capabilities of oscilloscopes. To obtain accurate voltage and current waveforms is a necessity before any waveform analysis can occur.
DA1855A Differential Amplifier have a low frequency cut-off of 40 Hz or higher, eliminating the ability to measure power at line frequencies Effects of Probes on Saturation Voltage Measurements To measure switching’s device saturation voltage while the device is operating in circuits requires the combination of several capabilities in the measurement system. First because the measurements are not ground referenced, thus differential voltage measurements are needed.
Operator’s Manual recovery performance is the oscilloscope or differential amplifier’s probe performance. Probes play an important role in device ON voltage measurements. They attenuate the voltage’s magnitude as well as provide a convenient way of connecting to the device under test. in addition to attenuating the input signal they also attenuate the rate of change of the oscilloscope or differential amplifier’s input signal.
DA1855A Differential Amplifier When viewed at 500 m/div, the same 400 V square wave shows the probe compensation to be slightly overpeaked. Figure 5 When the time/div is decreased to value normally used to view 20 to 150 kHz switchmode power conversion circuits, the slightly peaked LF compensation appears as a DC level shift. Figure 6 Viewing a power FET’s saturation voltage with the slightly peaked LF compensation makes the voltage appear to go negative.
Operator’s Manual Figure 7 Saturation Voltage Measurement To measure the saturation voltage of a power device in a flyback type switching power supply, connect the +INPUT probe to the drain and the –INPUT probe to the source of the switching device. There is no need to ‘float’ the oscilloscope. The probe connected to the –INPUT becomes the reference lead (same as black lead on a DMM).
DA1855A Differential Amplifier Gate Drive Voltage The main reason to measure the gate drive voltage is to assure rapid turn-on and turn-off and to assure that the transistor is fully saturated. Figure 8, Switching Power Supply with Upper and Lower FET Drive. Care must be taken when acquiring the switching’s device gate drive signal. In off-line switching power supplies, the switching devices are elevated to line potential. The DA1855A is ideally suited for this application with its high CMRR.
Operator’s Manual Rejecting the AC line voltage was no real challenge, but rejecting the drain to source signal is a real measure of system ability. The drain to source voltage rises over 245 Volt when the FET turns OFF. The maximum rate of rise of this signal is about 15 V/nsec followed by a ring at the bottom of the waveform. It will be necessary to adequately reject this signal if upper gate signal is the be measured accurately.
DA1855A Differential Amplifier Remote Control Commands When attached to a Teledyne LeCroy oscilloscope equipped with ProBus interface, the DA1855A Amplifier can be remotely controlled along with the other oscilloscope functions. The control interface can be either the RS-232 or IEEE-488 (GPIB) bus. The commands which control the amplifier are described below.
Operator’s Manual Gain Control Mode The DA1855A amplifiers have two modes for setting the amplifier gain and attenuation; Auto and Manual. (Refer to Gain Control Modes on page 47, Operation, for more information.) The gain control mode can be selected in the DA1855A control menu through the oscilloscope front panel, or through remote control by sending the commands which correspond tot the gain mode. Sending the PRx:ATTEN or PRx:GAIN commands will set the DA1855A amplifier to Manual gain control mode.
DA1855A Differential Amplifier Auto-Zero PRx:AUTOZERO, PRx:AZ Command Description The PRx:AUTOZERO command initiates an auto zero cycle of the differential amplifier to remove any offset drift from the output. The amplifier inputs will be disabled for a fraction of a second during the autozero cycle.
Operator’s Manual Coupling PRx:COUPLING, PRx:CPL Command/query Description The PRx:COUPLING command sets the input coupling for the + and – inputs of the differential amplifier. The valid arguments are AC, Ground and DC. The PRx:COUPLING? query returns the input coupling setting of the + and – inputs of the differential amplifier connected to the specified channel. The – input coupling is ignored when PVG Mode is set to VCOMP.
DA1855A Differential Amplifier Gain PRx:GAIN,PRx:GAI Command/Query Description The PRx:GAIN command sets the differential amplifier gain. The command will also switch the Atten/Gain control mode to Manual if it was in Auto. The valid arguments are 1 and 10. The PRx:GAIN? query returns the gain of the differential amplifier connected to the selected channel.
Operator’s Manual Offset PRx:OFFSET, PRx:OFST Command/Query Description The PRx:OFFSET command sets the Precision Voltage Generator (PVG) value of the DA1855A Differential Amplifier connected to the specified input channel. The oscilloscope channel offset is always set to 0 Volt. The maximum range and resolution is determined by the effective gain of the differential amplifier.
DA1855A Differential Amplifier Input-Resistance PRx:PINPUTR,PRx:PINR Command/Query Description The PRx:PINPUTR command sets the input resistance for both inputs of the differential amplifier. The valid arguments are 1M or 100M when the differential amplifier input attenuation is set to ÷1 and an attenuating probe is not being used. When an attenuating probe is attached to the differential amplifier, or the internal attenuation is set to ÷10, only 1M may be selected. The units of the arguments are Ohm.
Operator’s Manual Probe Attenuation PRx:PROBEATTENUATION?,PRxPATTN? Query Description The PRx:PROBEATTENUATION? query returns the attenuation value of the probe connected to the input of the DA1855A. Only probes which support probe code sensing will be correctly reported. Attenuation values of 1, 10, 100 or 1000 are sensed and can be reported. Probes which do not support probe code sensing will be reported having an attenuation of 1.
DA1855A Differential Amplifier Precision Voltage Generator PRx:PVGMODE,PRx:PVGM Command Query Description The PRx:PVGMODE command sets the operating mode of the Precision Voltage Generator (PVG) of the differential amplifier. The valid arguments are VCOMP, VDIFF and OFF. The PRx:PVGMODE? query returns the operating mode of the Precision Voltage Generator (PVG) of the differential amplifier connected to the specified channel.
Operator’s Manual Volt / DIV PRx:VOLT_DIV,PRx:VDIV Command/Query Description When used with the "PRx" argument for channel number, the VOLT/DIV command sets the vertical sensitivity at the probe tip. The effective gain of the differential amplifier, including any attenuating passive probes, is factored into the vertical sensitivity. The command will also set the Atten/Gain control mode to Auto if it was set to Manual mode.
DA1855A Differential Amplifier Performance Verification This procedure can be used to verify the warranted characteristics of the DA1855A Differential Amplifier. The recommended calibration interval for this Differential Amplifiers is one year. The complete performance verification procedure should be performed as the first step of annual calibration. Test results can be recorded on a photocopy of the Test Record provided in Appendix A.
Operator’s Manual Table 5, List of required Equipment Description Minimum Requirements Test Equipment Examples Wide Band Oscilloscope 500 MHz bandwidth 2 mV 200mv scale factors 1 ns - 10 μs sweep speed 2% vertical accuracy 50 Ω termination Teledyne LeCroy LT374 series oscilloscope Digital Multimeter DC: 0.01% accuracy AC: 0.
DA1855A Differential Amplifier Preliminary Procedure 1. Connect the DA1855A Differential Amplifier to an AC power source within the range listed in the Nominal Characteristics in the Specification section. 2. Allow at least 20 minutes warm-up time for the DA1855A and test equipment before performing the Verification Procedure. 3. Turn on the other test equipment and allow these to warm up for the time recommended by the manufacturer. 4.
Operator’s Manual Functional Check The functional check will verify the basic operation of the Differential Amplifier functions. It is recommended that the Functional Check be performed prior to the Performance Verification Procedure to assure that all other non-warranted functions perform as specified. To perform the functional check: Select channel 1 of the oscilloscope and set the input coupling to DC 50 Ω , vertical scale to 100 mV/div, timebase to 10 μsec/div and adjust the trace to screen center.
DA1855A Differential Amplifier 3. Bandwidth Limiting a. Press the 10 MHz BW Limit button on the front panel of the DA1855A and verify that the slope of the trace’s leading and trailing edge has decreased. b. Press the resp. 1 MHz and 100 kHz BW Limit buttons and verify that in each case that the slope of the leading and trailing edges decreases. c. Return to maximum bandwidth by pressing the FULL BW Limit button. 4. X10 Gain and ÷10 Attenuator a.
Operator’s Manual Figure 9, X1 Gail Accuracy j. Press the X1 GAIN button to remove any residual DC offset from the input. (A DC component may interfere with the RMS computation in some DMMs.) k. After the DMM has stabilized, record the reading to 100 μV resolution as ‘Amplifier Output Voltage’ in the Test Record. l. Divide the measured amplifier output voltage from step 1-k by the sine wave generator output voltage (amplifier input voltage) in step 1-f. Subtract the ratio from 1.
DA1855A Differential Amplifier 2. Check X10 Gain Accuracy NOTE: Because most DMMs do not provide the required accuracy on lower AC voltage ranges, the check for X10 Gain Accuracy uses a ratio technique with an external ÷10 attenuator. The actual attenuation of the attenuator is determined using higher amplitude signals. a. Disconnect the DA1855A amplifier output cable and the precision 50 Ω termination from the DMM. b.
Operator’s Manual Figure 10, X10 Gain Accuracy Setup. h. Remove the DMM cable from the BNC Tee and from the banana plug adapter on the DMM. i. Connect the 50 Ω termination end of the termination/attenuator/ BNC Tee combination on the sine wave generator cable to the Banana Plug adapter on the DMM. See Figure 11. Figure 11, X10 Gain Accuracy Setup. j. Record the DMM reading to 100 μV resolution as ‘Attenuator Output Voltage’ in the Test Record. NOTE: This reading should be approximately 200 mV.
DA1855A Differential Amplifier k. Divide the DMM reading in step 2-j into the output amplitude measured in step 2-g. This is the exact attenuation of the attenuator-termination combination. l. Record the result as ‘Exact Attenuation’ to four digit resolution in the Test Record. m. Disconnect the termination/attenuator/BNC Tee combination from the Banana Plug adapter on the DMM. n. Connect the terminated end of the termination/attenuator/ BNC Tee combination to the DA1855A +INPUT. o.
Operator’s Manual Figure 13, X10 Gain Accuracy Setup v. Divide the sine wave generator output voltage recorded in step 2-q by the exact attenuation factor recorded in step 2-l. This represents the actual voltage on the input of the amplifier. Record the result as ‘Amplifier Input Voltage’ in the Test Record. w. Multiply the amplifier input voltage as recorded in step 2-v by 10.0 to obtain the expected output voltage.
DA1855A Differential Amplifier 3. Check ÷10 Attenuator Accuracy a. Remove the DA1855A output cable/precision termination from the DMM. b. Remove the sine wave generator output cable/BNC Tee/ attenuator/termination combination from the +INPUT of the DA1855A. c. Remove the BNC Tee and attenuator from the cable but leave the standard 50 Ω termination connected. d. Connect the terminated output cable from the sine wave generator to the DMM using the BNC to Banana Plug adapter. Refer to Figure 14.
Operator’s Manual Figure 15, ÷10 Attenuator Accuracy Setup. l. Press the X1 GAIN button to autozero the amplifier. m. After the DMM reading has stabilized, record the reading as ‘Measured Amplifier Output Voltage’ to 100 μV resolution in the Test Record. n. Calculate the error by dividing the expected output voltage recorded in step 3-g by the measured amplifier output voltage recorded in step 3-m. Subtract this ratio from 1 and multiply by 100% to get the error in percent. o.
DA1855A Differential Amplifier 4. Check X1 Bandwidth and Calculate Rise Time a. Connect the DA1855A AMPLIFIER OUTPUT to channel 1 of the oscilloscope. b. Set the channel 1 input coupling to 50 Ω. NOTE: If the oscilloscope does not have an internal 50 input termination, insert the standard inline 50 termination between the cable and the oscilloscope input. Use the standard wide bandwidth 50 termination. The precision termination is not accurate at frequencies higher than 100 kHz. c.
Operator’s Manual i. Set the sine wave generator output frequency to 50 MHz. Be careful not to alter the output amplitude. NOTE: The displayed waveform will be compressed in time to form a solid rectangle. It is not necessary to alter the time/div setting as long as the peak amplitude can be measured. j. Slowly increase the output frequency of the leveled sine wave generator until the displayed amplitude decreases to exactly 4.2 divisions. This is a 3 dB reduction in amplitude. k.
DA1855A Differential Amplifier b. Set the DA1855A GAIN to X1, ATTENUATOR to ÷1. c. Set the leveled sine wave generator output frequency to 50 kHz. If necessary adjust the output amplitude for a display of exactly 6 divisions (300 mV) peak to peak. d. Change the output frequency to 10 MHz, taking care not to change the output amplitude. e. Measure the peak to peak output amplitude of the DA1855A. Record the reading to two digit resolution (xx0 mV) as ‘Amplifier Output Voltage at 10 MHz’ in the Test Record.
Operator’s Manual j. Verify that the channel 1 input coupling is set to DC and 1MΩ. k. Set the oscilloscope to display channel 1, the vertical sensitivity to 500mV/div, timebase to 50 ns/div and trigger source to external ÷10. If necessary, adjust the trigger level for a stable display. l. Set the leveled sine wave generator frequency to 10 MHz. m. Set the leveled sine wave generator output amplitude to exactly 2 Vp-p. (4 divisions on the oscilloscope). n.
DA1855A Differential Amplifier s. Verify that the oscilloscope is set to display channel 1 and the\ input coupling to DC and 50Ω. t. Increase the channel 1 vertical sensitivity to maximum. u. Verify that the oscilloscope is triggered on the Frequency Reference Signal Output of the sine wave generator. v. Measure the peak to peak amplitude. The displayed signal is the Common Mode Feedthrough.
Operator’s Manual b. Connect a BNC cable from the Frequency Reference Signal Output of the leveled sine wave generator to the External Trigger Input of the oscilloscope. (If the sine wave generator does not have a Frequency Reference Signal Output, insert a BNC Tee adapter into the Output connector and attach the External Trigger BNC cable to the BNC Tee.) Figure 20, LF CMRR Check Setup c. Set the oscilloscope to display channel 1, vertical scale to 5 V/div and time base to 10 ms/div. d.
DA1855A Differential Amplifier k. Set the oscilloscope to display channel 1, coupling to DC and impedance to 50 Ω and the vertical sensitivity as necessary to measure the amplitude of the displayed waveform. Refer to Figure 21 Figure 21, LF CMRR Check Setup l. The displayed signal is the Common Mode Feedthrough. (Use the oscilloscope ZOOM function and averaging if needed to increase the size of the displayed waveform and to reduce noise.) NOTE: This measurement needs to be made very carefully.
Operator’s Manual o. Calculate the Common Mode Rejection ratio (CMRR) at70 Hz by dividing the Differential Mode Gain at 70 Hz (1.0) by the Common Mode Gain (recorded in step 6-p). Record the result as ‘Common Mode Rejection Ratio at 70 Hz’ to two significant places in the Test Record. (Keep all of the trailing zeros.) p. Check that the CMRR at 70 Hz is greater than 50,000:1(94 dB). q. Remove the sine wave generator output cable from theDA1855A’s + input.
DA1855A Differential Amplifier aa. 100 kHz by dividing the Differential Mode gain at 70 Hz (1.0)by the Common Mode Gain recorded in step 6-bb. Record the result as ‘Common Mode Rejection Ratio at 100 kHz’ to two significant places in the Test Record. (Keep all of the trailing zeros.) bb. Check that the CMRR at 100 kHz is greater than 50,000:1(94 dB). cc. Remove all cables, terminations and adapters from the instruments. 7. Check the Precision Voltage Generator Accuracy a.
Operator’s Manual Performance Verification Test Record This record can be used to record the results of measurements made during the performance verification of the DA1855A Differential Amplifier. Photocopy this page and record the results on the copy. File the completed record as required by applicable internal quality procedures. The section in the test record corresponds to the parameters tested in the performance verification procedure.
DA1855A Differential Amplifier DA1855A Test Record Step Description Intermediate data Test Result X1 Gain Accuracy 1-f Sine Wave Generator Output Voltage _____________ V 1-k Amplifier Output Voltage _____________ V 1-m X1 Gain Error (Test limit ≤ 1%) _____________% X10 gain Accuracy 2-g Sine Wave Generator Output Voltage _____________ V 2-j Attenuator Output Voltage _____________ V 2-l Exact Attenuation _____________ 2-q Sine Wave Generator Output Voltage _____________ V 2-v Ampli
Operator’s Manual High Frequency CMRR Step Description Intermediate data 5-e Amplifier Output Voltage at 10 MHz _____________ V 5-f Differential Mode Gain at 10 MHz ___________ 5-w Common Mode Feedthrough at 10 MHz ___________ 5-y Common Mode Gain at 10 MHz ___________ 5-aa Common Mode Rejection Ratio at 10 MHz (Test limit: ≥ 1000:1) Test Result __________:1 Low Frequency CMRR 6-m Common Mode Feedthrough at 70 Hz _____________ V 6-n Common Mode Gain at 70 Hz ___________ 6-o Common
DA1855A Differential Amplifier Reference Differential Mode and Common Mode Differential amplifiers amplify the voltage difference which appears between the + input and – input. This voltage is referred to as the Differential Mode or Normal Mode voltage. The voltage component which is referenced to earth and is identical on both inputs is rejected by the amplifier.
Operator’s Manual The common mode frequency in these graphs is assumed to be sinusoidal. In real life applications, the common mode signal is seldom a pure sine wave. Signals with pulse wave shapes contain frequency components much higher than the repetition rate may suggests. As such, it is very difficult to predict actual performance in the application for CMRR versus frequency graphs.
DA1855A Differential Amplifier Certifications This section certifies the instrument’s Electromagnetic Compatibility (EMC), Safety and Environmental compliances. EMC Compliance EC DECLARATION OF CONFORMITY - EMC The amplifier meets intent of EC Directive 2004/108/EC for Electromagnetic Compatibility.
Operator’s Manual European Contact: Teledyne LeCroy Europe GmbH Waldhofer Str 104 D-69123 Heidelberg Germany Tel: (49) 6221 82700 AUSTRALIA & NEW ZEALAND DECLARATION OF CONFORMITY – EMC Amplifier complies with the EMC provision of the Radio Communications Act per the following standards, in accordance with requirements imposed by Australian Communication and Media Authority (ACMA): CISPR 11:2003 Radiated and Conducted Emissions, Group 1, Class A, in accordance with EN613261:2006 and EN61326-2-1:2006.
DA1855A Differential Amplifier Protection Class I: grounded equipment in which protection against electric shock is achieved by Basic Insulation and a connection to the protective ground conductor in the building wiring. Environmental Compliance END-OF-LIFE HANDLING The instrument is marked with this symbol to indicate that it complies with the applicable European Union requirements to Directives 2002/96/EC and 2006/66/EC on Waste Electrical and Electronic Equipment (WEEE) and Batteries.
Operator’s Manual Returning a Product Contact your local Teledyne LeCroy sales representative to find out where to return the product. All returned products should be identified by model number and serial number. Provide your name and contact number and if possible describe the defect or failure. In case of products returned to the factory, a Return Authorization Number (RAN) must be used. Contact your nearest Teledyne LeCroy office, or the New York Customer Care Center, to receive a RAN.
DA1855A Differential Amplifier Contact Teledyne LeCroy Teledyne LeCroy Service Centers United States and Canada World Wide Corporate Office Teledyne LeCroy Corporation 700 Chestnut Ridge Road Chestnut Ridge, NY, 10977-6499, USA Ph: 800-553-2769 / 845-425-2000 FAX: 845-578-5985 teledynelecroy.com Support: contact.corp@teledynelecroy.com Sales: customersupport@teledynelecroy.
