Passive Filter Design using PSpice
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This document describes the design process for passive low-pass filters, including: 1) Specifying the filter requirements such as cutoff frequency, passband ripple, and impedance specifications. 2) Calculating the component values using Butterworth or Chebyshev approximations. 3) Verifying the design meets specifications through simulation. 4) Optimizing components to standard values and adjusting other components. 5) Testing the design sensitivity to component tolerances. The process results in a filter circuit schematic with all component values that meets the initial specifications.
Passive Filter Design using PSpice
- 1. Passive Filter Design All Rights Reserved Copyright (C) Bee Technologies Corporation 2010 1 Design Services
- 2. Contents Slide # 1. Filter Design Category.............................................................................. 2. Passive Filter Design Flow- Chart............................................................. 3. Passive Low Pass Filter Design............................................................... 3.1 Specifications : .................................................................................. 3.2 Calculation : ...................................................................................... . 3.3 Verification : ...................................................................................... . 3.4 Optimization : .................................................................................... 3.5 Elements 3 4 5 5 6 7 8-9 10-11 12 13-15 16-20 21-23 2All Rights Reserved Copyright (C) Bee Technologies Corporation 2009
- 3. 1.Filter Design Category Available Filter Types • Low Pass Filter • High Pass Filter • Band Pass Filter • Band Reject Filter Approximation • Butterworth - No ripple - Smooth roll-off (rate of 20dB/decade for every pole) • Chebyshev - Pass-band ripple specification would be required. - Steeper roll-of Topology • Passive - High frequency range (> 1 MHz) - Source and load impedance specifications would be required • Active - Low frequency range (1 Hz to 1 MHz) - Unity-Gain Sallen-Key configuration (see Figure 1.0) Number of Order • 2nd -10th All Rights Reserved Copyright (C) Bee Technologies Corporation 2010 3
- 4. 2.Passive Filter Design Flow Chart All Rights Reserved Copyright (C) Bee Technologies Corporation 2010 4 2. Circuit design and calculation2. Circuit design and calculation 3. Verification3. Verification 4. Optimize with standard capacitor value4. Optimize with standard capacitor value 5. Elements test (± 5%)5. Elements test (± 5%) Meet the spec?Meet the spec? No Yes Satisfy?Satisfy? Yes YESYES Result : Filter circuit with all element values Result : Filter circuit with all element values Use Active FilterUse Active Filter 1.Customer’s specification 1.Customer’s specification No
- 5. 3.Passive Low Pass Filter Design (1/5) 3.1 Specifications : All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 5 Fr e que nc y 1 0 0KHz 1. 0MHz 10 MHz db ( v ( o ut ) ) - 4 0 - 3 0 - 2 0 - 1 0 0 Figure 1 Low-pass filter response and specification Pass-band Region Stop-band Region Pass-band edge frequency = 1 MHz Pass-band gain = -3 dB Stop-band edge frequency = 2.5 MHz Stop-band gain = -30 dB •Pass-band edge frequency : 1 MHz (fCutoff) - Pass-band gain : -3 dB •Stop-band edge frequency : 2.5 MHz - Stop-band gain : -30 dB •Load and Source Condition : - Source Type : Voltage - Filter Load Impedance : 50 Ω - Source Impedance : 50 Ω STEP1.Customer’s specification STEP1.Customer’s specification
- 6. 3.Passive Low Pass Filter Design (2/5) 3.2 Calculation : All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 6 Figure 2.1 Low-pass filter circuit with calculated element-values (Butterworth approximation). Figure 2.2 Low-pass filter circuit with calculated element-values (Chebyshev approximation). 0 C 2 1 0 . 6 6 n F R L 2 5 0 L 1 5 . 6 6 5 u H 1 2 R s 5 0 o u t 3 C 1 1 0 . 6 6 n F V s o u r c e 0 C 1 5 . 8 7 8 n F R L 5 0 o u t L 1 6 . 0 8 7 u H 1 2 L 2 1 4 . 7 u H 1 2 V s o u r c e R s 5 0 C 2 2 . 4 3 5 n F •L1=6.087uH •L2=14.7uH •C1=5.878nF •C2=2.435nF •L1=5.665uH •C1=10.66nF •C2=10.66nF STEP2. Circuit design and calculation STEP2. Circuit design and calculation
- 7. 3.Passive Low Pass Filter Design (3/5) All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 7 Figure 3 Response and specification of the calculated circuits. Fr equ en c y 1 00 KHz 1 . 0MHz 1 0MHz d b( v ( ou t ) ) d b ( v ( o u t 3 ) ) - 4 0 - 3 0 - 2 0 - 1 0 0 Butterworth (1MHz,-3dB) Chebyshev : (1MHz,-3dB) (2.5MHz,-34.8dB) (2.5MHz,-31.8dB) 3.3 Verification : • Frequency Response Simulation Pass-band Ripple (-2.81dB) •Pass-band edge frequencies : 1 MHz •Pass-band gains : -3 dB •Stop-band edge frequencies : 2.5 MHz •Stop-band gains : < -30 dB •Butterworth Approximation - No ripple - Roll-off rate is 80dB/decade •Chebyshev Approximation - Pass-band ripple : -2.81dB - Steeper roll-of with less passive component — Butterworth Approximation — Butterworth Approximation STEP3. Verification STEP3. Verification
- 8. 3.Passive Low Pass Filter Design (4/5) 3.4 Optimization : - Use standard capacitor values (E-12 Capacitor Values) - Optimize inductor values All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 8 •L1=6.7 uH •L2=15.4uH •C1=5.6nF •C2=2.2nF •L1=6.06uH •C1=10nF •C2=10nF Figure 4.1 Low-pass filter circuit with optimized element-values (Butterworth approximation). Figure 4.2 Low-pass filter circuit with calculated element-values (Chebyshev approximation). 0 C 1 5 . 6 n F R L 5 0 o u t L 1 6 . 7 u H 1 2 L 2 1 5 . 4 u H 1 2 V s o u r c e R s 5 0 C 2 2 . 2 n F 0 C 2 1 0 n F R L 5 0 L 1 6 . 0 6 u H 1 2 R s 5 0 o u t 3 C 1 1 0 n F V s o u r c e STEP4. Optimize with standard capacitor value (then verify) STEP4. Optimize with standard capacitor value (then verify)
- 9. Fr e q ue n c y 10 0 KHz 1. 0MHz 1 0MHz db( v ( ou t ) ) d b( v ( out 3) ) - 4 0 - 3 0 - 2 0 - 1 0 0 3.Passive Low Pass Filter Design (4/5) All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 9 Figure 5 Response and specification of the optimized circuits. Butterworth (1MHz,-3dB) Chebyshev : (1MHz,-3dB) (2.5MHz,-34.3dB) (2.5MHz,-31.8dB) 3.4 Optimization : • Frequency Response Simulation Pass-band Ripple (-2.62dB) •Pass-band edge frequencies : 1 MHz •Pass-band gains : -3 dB •Stop-band edge frequencies : 2.5 MHz •Stop-band gains : < -30 dB •Butterworth Approximation - No ripple - Roll-off rate is 80dB/decade •Chebyshev Approximation - Pass-band ripple : -2.62dB - Steeper roll-of with less passive component — Butterworth Approximation — Butterworth Approximation
- 10. 3.Passive Low Pass Filter Design (5/5) 3.5 Elements test : - ± 5% test for each element value. All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 10 •L1=6.7 uH (± 5%) •L2=15.4uH (± 5%) •C1=5.6nF (± 5%) •C2=2.2nF (± 5%) •L1=6.06uH (± 5%) •C1=10nF (± 5%) •C2=10nF (± 5%) Figure 6.1 Low-pass filter circuit with ± 5% of the element-values (Butterworth approximation). Figure 6.1 Low-pass filter circuit with ± 5% of the element-values (Chebyshev approximation). 0 C 1 5 . 6 n F R L 5 0 o u t L 1 6 . 7 u H 1 2 L 2 1 5 . 4 u H 1 2 V s o u r c e R s 5 0 C 2 2 . 2 n F 0 C 2 1 0 n F R L 5 0 L 1 6 . 0 6 u H 1 2 R s 5 0 o u t 3 C 1 1 0 n F V s o u r c e ± 5% ± 5% ± 5% ± 5% ± 5% ± 5% ± 5% STEP5. Elements test (± 5%) STEP5. Elements test (± 5%)
- 11. Fr eq ue nc y 100 KHz 1. 0 MHz 10 MHz d b( v ( out 3 ) ) - 4 0 - 2 0 0 Fr eq uenc y 1 00 KHz 1 . 0 MHz 10 MHz d b( v ( ou t ) ) - 4 0 - 2 0 0 3.Passive Low Pass Filter Design (5/5) All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 11 Figure 7 Response and specification when the element values are error with ±5%. 3.5 Elements test : • Frequency Response Simulation, compare to -5% and +5% of all element values. Butterworth — +5% — standard values — -5% Pass-band gain (-3 dB) Cutoff frequency : 0.9525M, 1M, 1.0527M Chebyshev — +5% — standard values — -5% Pass-band gain (-3 dB) Cutoff frequency : 0.9524M, 1M, 1.0526M
- 12. V s o u r c e 0 C 2 1 0 n F R L 2 5 0 L 1 6 . 0 6 u H 1 2 R s 2 5 0 o u t C 1 1 0 n F 0 C 1 5 . 6 n R L 5 0 o u t L 1 6 . 7 u 1 2 L 2 1 5 . 4 u 1 2 V s o u r c e R s 5 0 C 2 2 . 2 n 3.Passive Low Pass Filter Design 3.6 Result : • Low-pass filter circuit with all element values. All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 12 •L1=6.7 uH (± 5%) •L2=15.4uH (± 5%) •C1=5.6nF (± 5%) •C2=2.2nF (± 5%) •L1=6.06uH (± 5%) •C1=10nF (± 5%) •C2=10nF (± 5%) Figure 8.1 Low-pass filter circuit with all element-values (Butterworth approximation). Figure 8.1 Low-pass filter circuit all element-values (Chebyshev approximation). ± 5% ± 5% ± 5% ± 5% ± 5% ± 5% ± 5% Result : Filter circuit with all element values Result : Filter circuit with all element values
- 13. Fr equen c y 10KHz 100KHz 1. 0MHz 10MHz 100MHz db( v ( out ) ) - 80 - 60 - 40 - 20 0 4.Passive High Pass Filter Design (Example) Specifications : All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 13 Figure 9 High-pass filter response and specification Pass-band Region Stop-band Region Pass-band edge frequency = 1 MHz Pass-band gain = -3 dB Stop-band edge frequency = 0.4 MHz Stop-band gain = -30 dB •Pass-band edge frequency : 1 MHz (Cutoff frequency) - Pass-band gain : -3 dB •Stop-band edge frequency : 0.4 MHz - Stop-band gain : -30 dB •Load and Source Condition : - Source Type : Voltage - Filter Load Impedance : 50 Ω - Source Impedance : 50 Ω
- 14. V s o u r c e 0 C 2 1 n F R L 2 5 0 L 1 1 0 . 6 u H 1 2 R s 2 5 0 o u t C 1 1 n F 0 C 1 4 . 7 n F R L 5 0 o u t L 1 4 . 3 u H 1 2 L 2 7 . 1 u H 1 2 V s o u r c e R s 5 0 C 2 1 . 8 n F 4.Passive High Pass Filter Design (Example) Result : • High-pass filter circuit with all element values. All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 14 •C1=4.7nF (± 5%) •C2=1.8nF (± 5%) •L1=4.3uF (± 5%) •L2=7.1uH (± 5%) •L1=6.06uH (± 5%) •C1=10nF (± 5%) •C2=10nF (± 5%) Figure 9.1 High-pass filter circuit with all element-values (Butterworth approximation). Figure 9.1 High-pass filter circuit all element-values (Chebyshev approximation). ± 5% ± 5% ± 5% ± 5% ± 5% ± 5% ± 5%
- 15. Fr e quenc y 100KHz 1. 0MHz 10MHz db( v ( ou t ) ) - 40 - 20 0 Fr eque nc y 100KHz 1 . 0MHz 10MHz db( v ( out ) ) - 40 - 20 0 4.Passive High Pass Filter Design (Example) All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 15 Figure 10 Response and specification when the element values are error with ±5%. Elements test : • Frequency Response Simulation, compare to -5% and +5% of all element values. Butterworth — +5% — standard values — -5% Pass-band gain (-3 dB) Cutoff frequency : 0.952M, 1M, 1.052M Chebyshev — +5% — standard values — -5% Pass-band gain (-3 dB) Cutoff frequency : 0.9523M, 1M, 1.0526M Pass-band Ripple (-2.7dB)
- 16. •Low end pass band frequency : 1 MHz (fC-L) - Pass-band gain : -3 dB •Low end stop band frequency : 0.4 MHz - Stop-band gain : < -25 dB •High end pass band frequency : 3 MHz (fC-H) - Pass-band gain : -3 dB •High end stop band frequency : 5 MHz - Stop-band gain : < -25 dB •Load and Source Condition : - Source Type : Voltage - Filter Load Impedance : 50 Ω - Source Impedance : 50 Ω Fr e qu e nc y 1. 0MHz 10 MHz3 00 KHz d b( v ( ou t ) ) - 40 - 30 - 20 - 10 0 5.Passive Band Pass Filter Design (Example) Specifications : All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 16 Figure 11 Band-pass filter response and specification Pass-band Region Low end pass band frequency = 1 MHz Pass-band gain = -3 dB Low end stop band frequency = 0.6 MHz Stop-band gain < -25 dB Stop-band RegionStop-band Region High end pass band frequency = 3 MHz High end stop band frequency = 0.6 MHz
- 17. L 4 7 . 3 u H 1 2 C 4 1 . 2 n 0 R L 5 0 o u t V s o u r c e R s 5 0 L 1 3 u H 1 2 C 1 2 . 7 n L 2 2 . 8 u H 1 2 L 3 7 . 8 u H 1 2 C 2 2 . 7 n C 3 1 . 2 n 5.Passive Band Pass Filter Design (Example) Result (Butterworth approximation) : • High-pass filter circuit with all element values. All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 17 •L1 = 3uH (± 5%) •L2 = 2.8uH (± 5%) •L3 = 7.8uH (± 5%) •L4 = 7.3uH (± 5%) •C1 = 2.7nH (± 5%) •C2 = 2.7nF (± 5%) •C3 = 1.2nF (± 5%) •C4 = 1.2nF (± 5%) Figure 12 Band-pass filter circuit with all element-values (Butterworth approximation). ± 5% ± 5% ± 5% ± 5% ± 5% ± 5% ± 5% ± 5%
- 18. Fr equenc y 1. 0MHz 10MHz300KHz db( v ( out ) ) - 40 - 30 - 20 - 10 0 5.Passive Band Pass Filter Design (Example) All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 18 Figure 13 Response and specification when the element values are error with ±5%. Elements test (Butterworth approximation) : • Frequency Response Simulation, compare to -5% and +5% of all element values. Butterworth — +5% — standard values — -5% Pass-band gain (-3 dB) fC-L: 0.95M, 1M, 1.05M fC-H: 2.876M, 3M, 3.178M
- 19. 0 R L 5 0 o u t V s o u r c e R s 5 0 L 1 1 2 . 3 u 1 2 C 1 6 8 0 p L 2 7 u 1 2 L 3 1 2 . 3 u 1 2 C 2 1 . 2 n C 3 6 8 0 p 5.Passive Band Pass Filter Design (Example) Result (Chebyshev approximation) : • High-pass filter circuit with all element values. All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 19 •L1 = 12.3uH (± 5%) •L2 = 7uH (± 5%) •L3 = 12.3uH (± 5%) •C1 = 680pF (± 5%) •C2 = 1.2nF (± 5%) •C3 = 680pF (± 5%) Figure 14 Band-pass filter circuit with all element-values (Chebyshev approximation). ± 5% ± 5% ± 5% ± 5% ± 5% ± 5%
- 20. Fr equenc y 1. 0MHz 10MHz300KHz db( v ( out ) ) - 40 - 30 - 20 - 10 0 5.Passive Band Pass Filter Design (Example) All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 20 Figure 15 Response and specification when the element values are error with ±5%. Elements test (Chebyshev approximation) : • Frequency Response Simulation, compare to -5% and +5% of all element values. Chebyshev — +5% — standard values — -5% Pass-band gain (-3 dB) fC-L: 0.952M, 1M, 1.052M fC-H: 2.8812M, 3M, 3.184M Pass-band Ripple (-2.63dB)
- 21. Fr equenc y 1. 0MHz 10MHz300KHz db( v ( out ) ) - 40 - 30 - 20 - 10 0 •Low end pass band frequency : 1 MHz (fC-L) - Pass-band gain : -3 dB •Low end stop band frequency : 1.4 MHz - Stop-band gain : < -25 dB •High end pass band frequency : 3 MHz (fC-H) - Pass-band gain : -3 dB •High end stop band frequency : 2.2 MHz - Stop-band gain : < -25 dB •Load and Source Condition : - Source Type : Voltage - Filter Load Impedance : 50 Ω - Source Impedance : 50 Ω 6.Passive Band Reject Filter Design (Example) Specifications : All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 21 Figure 16 Band reject filter response and specification Pass-band Region Low end pass band frequency = 1 MHz Pass-band gain = -3 dB Low end stop band frequency = 0.6 MHz Stop-band gain < -25 dB Stop-band Region High end pass band frequency = 3 MHz High end stop band frequency = 0.6 MHz Pass-band Region
- 22. 0 R L 5 0 V s o u r c e R s 5 0 L 1 3 . 5 5 u 1 2 o u t C 1 2 n L 2 2 . 2 u 1 2 C 2 3 . 3 n L 3 9 u 1 2 C 3 1 . 2 n 6.Passive Band Reject Filter Design (Example) Result : • High-pass filter circuit with all element values. All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 22 •L1 = 3.55uH (± 5%) •L2 = 2.2uH (± 5%) •L3 = 9uH (± 5%) •C1 = 2nH (± 5%) •C2 = 3.3nF (± 5%) •C3 = 1.2nF (± 5%) Figure 17 Band-reject filter circuit with all element-values ± 5% ± 5% ± 5% ± 5% ± 5% ± 5%
- 23. Fr equenc y 1. 0MHz 10MHz300KHz db( v ( out ) ) - 40 - 30 - 20 - 10 0 6.Passive Band Reject Filter Design (Example) All Rights Reserved Copyright (C) Bee Technologies Corporation 2009 23 Figure 13 Response and specification when the element values are error with ±5%. Elements test : • Frequency Response Simulation, compare to -5% and +5% of all element values. Butterworth — +5% — standard values — -5% Pass-band gain (-3 dB) fC-L: 0.9457M, 1M, 1.0456M fC-H: 2.873M, 3M, 3.175M