Laboratory on Filter Circuits Dr. Lynn Fuller

Transcription

1 ROCHESTER INSTITUTE OF TECHNOLOGY MICROELECTRONIC ENGINEERING Laboratory on Filter Circuits Dr. Lynn Fuller Webpage: 82 Lomb Memorial Drive Rochester, NY Tel (585) MicroE webpage: Lab_Filter_Circuits.ppt Page 1

2 OUTLINE Op Amp Frequency Response Active Filters References Homework Page 2

3 OPERATIONAL AMPLIFIER DC CHARACTERIZATION +V=+6 Vout +6 Vin - + Vout 0 Slope = Gain -V= mV Vos Vin +20mV Set up the HP 4145 to sweep the Vin from -20 mv to +20 mv in 0.001V steps. Measure Gain and Input offset voltage. 0 Page 3

4 MEASURED OPEN LOOP DC GAIN SMU1 100k 1k Vi v Vout SMU2-6v Gain = slope x 100 = 66,000 = 96 db Page 4

5 FREQUENCY RESPONSE OF AN OP AMP +V Vin C1 100k 1k 100k Rb v -6v Vout -V Adjust Rb to give Vout = zero with Vin = zero, Then use a network analyzer to collect data for Gain vs Frequency Page 5

6 NETWORK ANALYZER Q uick Measurement Setup for 3577A Network Analyzer (by Jirachai Getpreecharsawas) Magnitude Plot: 1. Press INPUT button and select input A 2. Press DISPLY FCTN button and select LOG MAG 3. Press FREQ button and select STOP FREQ Note: Other options are also available. 4. Press AMPTD button and adjust the amplitude if necessary, say 20 dbm 5. Press RES BW and select an appropriate frequency resolution, say 100 Hz Note: Sweep time might need to be adjusted so that it is higher than the settling time required for each Res BW, see table* below. * Instruction Manual for 3577A Network Analyzer, pp If applicable, press SWEEP TYPE button and select LOG FREQ SWEEP to display x-axis (freq) in log scale Note: You might need to readjust the frequency range again by pressing FREQ button! Tip: Turning the knob will move the Marker along the trace (data readout). Network Analyzer Phase Plot: 1. Press TRACE 2 button 2. Press INPUT button and select input A 3. Press DISPLY FCTN button Rochester and select Institute PHASE of Technology 4. If needed, adjust the frequency Microelectronic range using FREQ Engineering button Obtain a plot using software Agilent Data Capture 2: 1. Go to Programs > Agilent IntuiLink > IntuiLink Data Capture Application 2. Click Instrument tab, choose 3577A if not selected, accept default setting, and click OK. 3. Click Get Data icon, the 2nd icon from the right, to open a plot window if no plot shown Page 6

7 AC TEST RESULTS ROCHESTER INSTITUTE OF TECHNOLOGY MICROELECTRONIC ENGINEERING LFF OPAMP.XLS FILE3B LOT F OPAMP TEST RESULTS Frequency Gain Vout Vin hz db V mv Gain db Op Amp Frequency Response Fre quency Hz GBP = 500,000 Hz Page 7

8 LOW PASS FILTER Vin R1 - + C2 R2 Vout Derive an expression for Vo/Vin Plot 20Log 10 (Vo/Vin) vs frequency Verify using SPICE Verify by building the circuit Vo/Vin = -R2/R1 ω = 2 π f ω1 = 1/R2C j ω/ω1 1 SR2C2 + 1 f Page 8

9 HIGH PASS FILTER Vin C1 R1 - + R2 Vout Derive an expression for Vo/Vin Plot 20Log 10 (Vo/Vin) vs frequency Verify using SPICE Verify by building the circuit Vo/Vin = -R2/R1 ω = 2 π f ω1 = 1/R1C1 j ω/ω1 1 + j ω/ω1 SR1C1 SR1C1 + 1 f Page 9

10 GENERAL FILTER Vin C1 R1 - + C2 R2 Derive an expression for Vo/Vin Plot 20Log 10 (Vo/Vin) vs frequency Verify using SPICE Verify by building the circuit Vout Vo/Vin = -R2/R1 SR1C1 + 1 SR2C2 + 1 ω = 2 π f ω1 = 1/R1C1, ω2 = 1/R2C2 = -R2/R1 1 + j ω/ω1 1 + j ω/ω2 Page 10

11 COMBINATIONS OF FILTERS Vo/Vin = -R2/R1 1 + j ω/ω1 1 + j ω/ω2 Two General Filters in series General ω1, ω2 General ω3, ω4 Vo/Vin = -R2R4/R1R3 1 + j ω/ω1 1 + j ω/ω2 1 + j ω/ω3 1 + j ω/ω4 2 nd Order low-pass, high-pass, bandpass, bandrejection and all pass filter Page 11

12 SKETCH OF VARIOUS FILTER FREQUENCY RESPONSE Vo/Vin = -R2R4/R1R3 ω1 = ω3 < ω2 = ω4 1 + j ω/ω1 1 + j ω/ω2 1 + j ω/ω3 1 + j ω/ω4 ω2 = ω4 < ω1 = ω3 ω1 < ω2 < ω4 < ω3 ω2 < ω1 < ω3 < ω4 Page 12

13 REFERENCES 1. Switched Capacitor Circuits, Phillip E. Allen and Edgar Sanchez-Sinencio, Van Nostrand Reinhold Publishers, Active Filter Design Using Operational Transconductance Amplifiers: A Tutorial, Randall L. Geiger and Edgar Sanchez-Sinencio, IEEE Circuits and Devices Magazine, March 1985, pg Microelectronic Circuits, 5 th Edition, Sedra and Smith 4. CMOS Analog Circuit Design, Phillip Allen, Douglas Holbert, Holt, Rinehard and Winston, 1987, pg Page 13

14 LABWORK FILTERS Build the three 1 st order active filters described below (corners need not be exact) and show they work by measuring the small signal gain at various frequencies. Use the network analyzer to obtain a bode plot for the low pass filter. 1. Build a low pass filter with gain of 10 and corner frequency ~20K hz 2. Build a high pass filter to have a gain of 10 and corner frequency of ~1000 hz. 3. Build a band pass filter to pass frequencies between 1K to 20Khz. Page 14