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1. Figure 1 Schematic circuit for Common Emitter Amplifier 2 Measure the DC bias points using Digital Multimeter Make sure the amplifier is biased properly and operating in the forward active region 3 Connect the input signal of the amplifier at the base of the transistor to one the channel on the oscilloscope say Channel 1 Connect the output signal of the amplifier at the collector of the transistor to other channel on the oscilloscope say Channel 2 These signals are AC signals superposed on the DC bias signal The DC signal will normally be large compared to the AC signals and one may not able to see the AC signals clearly The AC signal without the DC component can be displayed by setting the coupling to AC To do this select Vertical Vertical Setup A graphical palette appears similar to the Figure 2 Select coupling as AC for both the channels 4 The input waveforms can be noisy because of its small amplitude of the signals To average out the noise select Horiz Acq Acquisition Average HiRes Figure 3 shows the acquired input output waveforms Channel 1 yellow trace displays the input waveform and channel 2 blue trace displays the output waveform Copyrighted by Arizona State University Revised 8 24 2004 File Edit Yertical Horz Acqg Trig Display Cursors Measure Math Utilities Help Tek Run Sample 0 Jun 03 04 12 08 Buttons Ch2 Position Ch2 Scale j Display Position Termination oe
2. Vertical Zoom Offset Figure 2 AC Coupling Setup File Edit Vertical Horiz Acqg Trg Display Cursors Measure Math Utilities Help File Edit Vertical Horiz Acqg Trg Display Cursors Measure Math Utilities Help Average 0 Jun 03 04 06 26 Buttons Tek Run Sample 0 Jun 03 04 03 31 Num Averages Acquisition Mode Wim Sample Database Pk Detect Hi Res 7 Average Envelope y n j i fi of Wims i M 40 0ps 1 25MS s 600ns pt amp Ch2 00y M 40 0ps 1 25MS s 800ns pt a Sample Acquisition Mode b Average Acquisition Mode Figure 3 Input and Output waveforms To measure the gain of the amplifier we need the amplitude of the input and output signals One can measure the input and output signal amplitudes manually using the cursors Using the TDS7000 Series DPOs these measurements can be obtained automatically To do this Select Measure Measurement Setup Select amplitude and the source as shown in the Figure 4 Copyrighted by Arizona State University Revised 8 24 2004 File Edit Vertical Horiz 4cqg Trig Display Cursors Measure Math Utilities Help 0 Jun 03 04 22 07 B aa Buttons uttons Num Averages 100 Ml 40D ys 1 25MS s 800risipt AC f 1 8m Ampl Time More Source Measurements Setup Display Amplitude MER Ch Math Ref Amplitude Ch1 Ref Leys on Channel Amplitude Ch2 7 Bating Snapshot Ti Statistics Histogram n e Figure 4 Measuring the ampli
3. Setting up the Oscilloscope 1 From the Functions Palette open Instrument I O Instrument Drivers gt tkpds7k and find Initialize vi Set Vertical Parameters vi Set Wim Display vi You will need two each for the Set Vertical Parameters vi and Set Wfm Display vi one for the channel connected to the input signal of the amplifier and the other for the output signal Place Measurement source vi Measurement Type vi Measurement State vi Again you will need two each of these vis one for measuring input amplitude and the other for output amplitude Place Autoset vi Set Acquisition Mode vi Set Horizontal Scale vi Set Trigger A Edge Parameters vi Set Horizontal RecLength vi Place two of Get Measurement Value vi Close vi Create a formula node and enter the expression for gain Create constants controls and indicators and connect as shown in the Figure 8 The front panel can be arranged as shown in the Figure 9 Revised 8 24 2004 Copyrighted by Arizona State University From the error out of close vi Oscilloscone Hscale From jor Function Generator Function Generator name Channel Setup Fert Ea Feri EE a e __ Measi corresponds bo input Meas corresponds bo output Scale and trigger setup Measurements and Calulation of gain oy youtlyvin Avde 20 logi ays pain fain dB Figure 8 VI part for the oscilloscope Copyrighted by Arizona State University Revised 8 24 2004
4. and has worked with instrument drivers before In this section the automation for the gain measurement is described using the TDS7104 digital phosphor oscilloscope coupled with LabVIEW software connected via GPIB to an AFG310 arbitrary function generator and PS2521G DC power supply The programming should be similar for other instruments Download the required drivers for these instruments and make sure you are able to see these devices in the Functions Palette Instrument I O Instrument Drivers To determine whether the drivers are installed and working properly open Getting Started vi of the instrument and run it Setting up the PS2521G DC Power Supply 1 From the Functions Palette open Instrument I O Instrument Drivers gt tkps252x VIs and find Initialize vi Configure OVP OCP vi Configure Current Voltage vi Output on off vi Close vi and place them on the block diagram 2 From the Tools Palette select Connect Wires right click on the resource name of Initialize vi and create a control by selecting Create Control Similarly create a control for ovp limit constants for ocp and channel of Configure OVP OCP vi Connect the rest as shown in the Figure 6 Controls are inputs to the vi and indicators are the outputs of the vi The controls can be used instead of constants and corresponding values must be set via the front panel 3 Run the vi to see if the Power Supply is controlled properly and to check for any errors
5. or digital phosphor oscilloscope DPO can also digitally process the signal before it is displayed making complex measurements much easier For example you can use the oscilloscope s average mode to remove the effects of random noise to make precise amplitude measurements The averaging function smoothes out the waveform by averaging multiple waveforms while the high resolution mode filters the samples taken during an acquisition to create a higher resolution lower bandwidth signal The average and high resolution acquisition modes are useful when measuring signals of small amplitudes Other types of acquisition modes include peak detect and envelope Refer to the Oscilloscopes User Manual for more information In this paper we describe the setup to perform two of the most common analog circuit laboratory experiments Lab Il Measuring the Gain of a Common Emitter Amplifier Lab Il Frequency Response of a Common Emitter Amplifier Copyrighted by Arizona State University Revised 8 24 2004 Lab I Measuring the Gain of a Common Emitter Amplifier One of the important measurements of an amplifier is its gain The following is the setup to measure the gain of a common emitter amplifier in addition to the description of the automated measurement using LabVIEW Setup 1 Set up the circuit as shown in the Figure 1 The resistors R1 R2 are just to attenuate the signal so that a small input signal few mVs is applied to the amplifier
6. Copyrighted by Arizona State University Revised 8 24 2004 Development of Analog Circuit Labs using TDS7000 Series Digital Phosphor Oscilloscopes In this lab paper we describe the use of TDS7000 Series digital phosphor oscilloscopes DPOs in the development of analog circuit laboratory experiments for senior classes These experiments are designed to offer Practical insight into the topics covered in the class Solid understanding of issues involved in building the actual circuits designed in the class like proper biasing and debugging Experience with measurement equipment similar to the equipment used in the industry The TDS7000 Series simple user interface and built in automated waveform measurements allow the students to take measurements easily and accurately These measurement features coupled with the oscilloscope s calculator type math features can be used to evaluate expressions involving the measurements taken The TDS7000 Series spectrum analyzer style interface allows students to perform frequency domain analysis Acquisition Before taking any measurements you must first acquire a signal or waveform The basic acquisition mode of a digital oscilloscope is the sample mode where the waveform is sampled in time and the amplitude of each sample is digitized and displayed With the use of interpolation these samples can be connected to create a continuous waveform display A digital storage oscilloscope DSO
7. cation software like LabVIEW LabWindow CVI Matlab or high level application development languages like C and Visual Basic eliminating the need for separate computers Copyrighted by Arizona State University Revised 8 24 2004 Lab Il Frequency Response of Common Emitter Amplifier The traditional way to observe the frequency response of a common emitter amplifier is to apply the input at different frequencies take measurements and plot the response The TDS7000 Series Fast Fourier Transform FFT feature and intensity graded display coupled with the AFG310 320 arbitrary function generator s sweep mode provide an easy way to observe the frequency response Note This is possible only when the harmonics at a frequency in the range of interest is less than the fundamental at that frequency for all frequencies of interest The function generator s sweep mode generates signals of different frequencies within a time duration called sweep time When the function generator output is connected to the setup as shown in the Figure 1 the response of the amplifier to various frequencies can be observed on the oscilloscope using the FFT feature one ata time The oscilloscope s intensity graded display can be used to more easily interpret the response of all the frequencies Setting up the Function Generator in Sweep Mode 1 Press MODUL button on the front panel Use v and buttons to scroll through until SWP Sweep mode is displayed and pres
8. resource name Oscilloscope JaPIBS 1 INSTR Channel setup Measurement setup i p amplitude i i i 5 62500m Channel 1 Channel Z Measrument 1 Measurement 2 op amplitude Display DUNES Type Display 512 00m Coupling CHI Amplitude 1 on lt i gain gain dE bioz fasies Figure 9 Oscilloscope front panel Other Features of the Oscilloscope The built in Windows based platform of the TDS7000 Series oscilloscopes simplifies the transfer of data from the oscilloscope to a personal computer PC Waveforms can be exported as bitmap or jpeg files and used directly in reports or presentations using the export command under the File menu The Select for Export command allows you to specify whether to export numerical waveform and measurement data or bitmap images of the graticule or entire screen area Numerical data can also be exported for further analysis The Export Setup command allows you to choose the file format bitmap bmp and jpeg jpg formats are available for the waveforms while txt csv and dat formats are available to export numerical data to applications including word document spreadsheets Excel Lotus 1 2 3 Quattro Pro and mathematical applications MATLAB Mathcad Finally the Export command allows you to save the file onto the system or disk These features allow you to document waveforms and test results easily These Windows based oscilloscopes integrate the power and flexibility of appli
9. s enter 2 Inthe sweep mode enter three parameters SWP START start frequency SWP STOP stop frequency and SWP TIME sweep time Use and to scroll through until the desired parameters are displayed enter the parameter and press enter Enter SWP START as 1Hz SWP STOP as 200Hz and SWP TIME as 50s Setting up the Oscilloscope 1 Select Math Spectral Setup 2 Select Magnitude and the source as channel 2 3 Enter the sampling rate more than the Nyquist Rate say 1ks span frequency as 250Hz and center frequency as 125Hz 4 Select Display Display Format Infinite Persistence The above setup is for the low frequency response The high frequency response can be obtained similarly by the changing the frequencies appropriately Figure 10 shows the frequency response of the amplifier Copyrighted by Arizona State University Revised 8 24 2004 File Edit Vertical Horiz Acq Ing Display Cursors Measure Math Utilities Help File Edit Vertical Horiz Acq Trig Display Cursors Measure Math Utilities Help Tek Run Hi Res 0 Jun 03 05 26 30 Buttons Tek Run Hi Res 07 Jun 03 05 39 35 Buttons Curs1 Pos 3 4dB Curs1 Pos 200 0mdB Curs2 Pos Curs2 Pos 2 8dB 00 0mdB A 2 0ps 25 0MS4s 40 0ns pt f 1 8mY M 100ms 500S s 2 0rms pt 5 1 8mY a Low frequency response b High frequency response Figure 10 Frequency response of the amplifier The automation of this experiment can be done similar to the one
10. shown in the previous experiment by placing the vis responsible for generating input frequency and the measurements in a loop Copyrighted by Arizona State University Revised 8 24 2004 Conclusion This paper demonstrates the use of the TDS7000 Series digital phosphor oscilloscopes to develop analog circuit laboratory experiments The oscilloscope s measurement and math features allow you to easily measure the gain of the amplifiers The intensity graded display coupled with the sweep mode of the AFG3x0 function generators provides a way to observe the frequency response in a single step The waveforms numerical data and measurements can be moved to the Windows based platform within the oscilloscope for documentation or further analysis The Windows based oscilloscope integrates the applications software into the instruments which can be used to automate the equipment s to perform a sequence of tasks and analyze and process acquired signals
11. tude of the signals Gain is calculated as the ratio of the output to the input amplitudes The Math feature allows you to calculate the gain from the measurements taken Select Math Math setup and enter the expression for the gain as shown in the Figure 5 The expression is displayed as the waveform The gain can be measured as the mean of the Math waveform To calculate the mean setup the measurement as described earlier but select Math as the source instead of channel File Edit Vertical Horiz 4cqg Trig Display Cursors Measure Math Utilities Help Tek Run Hi Res 0 Jun 03 04 24 29 Ni sf 0ps 1 25MS s SOOS At A 1 8mY Time Freq Meas NEU ae O LOG Meas2 Meas 1 EE arao om Amplitude ch2 E Operands Ch Mathi Ref eel Ka 8 ag BRO hi PE EA CHS EJ a Cancel m E Oe Figure 5 Equation Editor Copyrighted by Arizona State University Revised 8 24 2004 Automating Measurements Using LabVIEW Software You can use LabVIEW software on the TDS7000 Series Windows based oscilloscopes to automate the equipment s connected to the oscilloscope to perform a sequence of tasks and analyze and process the measurements taken The automation greatly alleviates several common laboratory problems such as insufficient laboratory time bad laboratory data and calculations The automation increases student productivity by accelerating routine data taking This section assumes that the reader has some familiarity with the LabVIEW environment
12. up to this point instrument descripter IGPIB 5 output t on owp limit ee E 7 00 DELK OBL voltage limit current limit 6 00 51 000 a Block diagram b Front panel Figure 6 VI part for DC power supply Copyrighted by Arizona State University Revised 8 24 2004 Setting up the AFG310 AFG320 Arbitrary Function Generator 1 From the Functions Palette open Instrument I O Instrument Drivers kafg3x0 and find Initialize vi Configure Standard Waveform vi Configure Output Enabled vi Close vi and place them on the block diagram 2 Create controls constants and connect the vis placed as shown in the Figure 7 Connect the error out of the DC Power Supply to the error in of the Function Generator 3 Create a formula node and enter the expression to get the Horizontal Scale required for the oscilloscope to capture about five cycles 4 Run the vi to see if the Function Generator is also controlled properly and to check for any errors up to this point Hscale will be used to set the resource name GPIB 1 INSTA Prom the error out of close vi Horizontal scale of the scope GPESINSTA of DC Power Supply Frequency 1000 Hz 7 AAR E T 0 5 4 amplitude 1 00 saim frequency 1000 Hz output enabled ON OW amplitude 1 00 a Block diagram b Front panel Figure 7 VI part for Arbitrary Function Generator Copyrighted by Arizona State University Revised 8 24 2004

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