Analog Signal Processing

1
Analog Signal Processing

• Filter Examples
• Design 1-pole LP to reduce specific signal
• Design 1st Order HP to reduce 60 Hz noise
• 2nd Order LP and loading
• 4th Order Butterworth
• Intro to Opamps
• Characteristics
• Specifications
• Basic circuits

2
Derivation Review
Final Result remember square root of sum
of squares
Remember that the cutoff frequency of a 1st order
RC filter is
3
Design a 1-pole LPF to reduce the undesired 50KHz
signal by 32 dB in voltage. Also, find the cutoff
frequency of the filter
And solving for Vout/Vin yields .025119
Remember that
Now, solving the top equation for fc you get fc
1256 Hz
4
Design a 1-pole LPF to reduce the undesired 50KHz
signal by 32 dB in voltage. Also, find the cutoff
frequency of the filter
Since
Choose a convenient value for the capacitance,
say .01 uF, then solve for the required
resistance. Thus, R 12.67 kO
5
Freq. Response
dB
6
Design a 1st order HP filter to reduce 60 Hz
noise by 20 dB in Power
7
Design a 1st order HP filter to reduce 60 Hz
noise by 20 dB in Power
fc 180 Hz
If you choose C 1 uF then R884 O
8
Frequency Response
dB
9
2nd Order LP Filter
Figure 1 For a 1st order LP filter fc 1256 Hz
Figure 2 For a 1st order LP filter fc 1256 Hz
Ideal
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Transfer Functions
To calculate the transfer function you need to
find Vout/Vin which is quite difficult with
complex numbers.
This transfer function is just the transfer
function of one filter squared.
At f 1256 this equation equals ½.
20Log10(.5)-6dB
11
2nd Order Filter Response
dB
12
Passive Butterworth filtershttp//members.aol.com
/maxfro/private/butter.html
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4th order passive filter
14
4th Order Butterworth-50 ohm
15
Frequency Response
16
OpAmps
http//socrates.berkeley.edu/phylabs/bsc/PDFFiles
/bsc7.pdf
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Op Amp specifications
http//www.national.com/pf/LM/LM741.html
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Basic Op Amp CircuitsInverting op amp
http//www.es.oersted.dtu.dk/c49102/Circuit03.htm
l
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Basic Opamp CircuitsVoltage Follower
(non-inverting)
http//www.es.oersted.dtu.dk/c49102/javalab.html
examples
20
More opamp circuits
VLoad-5V1-2V2-V3
VLoad(1Rf/R1)Vin
VLoad(R2/R1)(V2-V1)
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Summary

• Filter Examples
• Design 1-pole LP to reduce specific signal
• Design 1st Order HP to reduce 60 Hz noise
• 2nd Order LP and loading
• 4th Order Butterworth
• Intro to Opamps
• Characteristics
• Specifications
• Basic circuits