Low Pass Filter - Classification
- 1. Low Pass Filter SIES Grad. School of Tech : S.E. – EXTC A-3 Atharva Karnik (117A2048)
- 2. What is a Low Pass Filter ? • A circuit arrangement which allows signals of frequencies ranging from 0 Hz to fH Hz (fH = higher cut-off frequency) • Signals of frequencies greater than fH Hz are rejected • Consists of one resistive (Resistor) and one reactive (Capacitor) component • High attenuation is offered at frequencies beyond fH Hz
- 3. RC Low Pass Filter • Simplest L.P.F. consists of 1 Resistor and 1 Capacitor. In this type of arrangement, input (Vin) is applied to series combination of resistor (R) and capacitor (C) but the output signal (Vout) is taken across capacitor only.
- 4. Transfer Function of 1st order LPF By transforming the circuit into frequency domain, we get the transfer function of L.P.F. as follows. Thus, when frequency increases, transfer function decreases.
- 5. Classification of LPF as System • As it doesn’t have any active elements, LPF is Linearly Time Invariant system • Ideally LPF should be non-causal. But practically it is Causal system • Ideally LPF should be unstable due to charge storing capability of capacitor. But in practice, it is Stable system • It is a Static system as capacitor doesn’t have any discharge path • It is neither Inversible nor Non-inversible system as only low frequency components can be recovered from output while high frequency components are lost in the form of heat energy.
- 6. Classification of LPF Signals • Periodicity of output signal is dependent upon application. • Practically it is neither Even nor Odd as such signals don’t exist. • Neither Deterministic nor Non-Deterministic as it depends upon the input signal applied to the system. • Practically output is always Power signal as it remains finite even at infinite values of time. • Basically, LPF passes every signal which has lower frequency than fc. Thus, signal properties depend upon only the values of components used for addition of noise and thus affecting signal quality.
- 7. Applications of Low Pass Filters • Audio applications such as passing signals which have audio frequency only • Signal processing in equalizers where operations are needed to be performed on specific frequency signals • Reception of baseband signals in superheterodyne receivers e.g. GMRT telescopes • Anti-aliasing filter in Image Processing • Used as Integrator in few applications • Telephone system uses LPF to convert audio frequencies of speaker to a band limited 0.3 KHz to 3.4 KHz Voice Band Signal
- 8. References • http://www.etti.unibw.de/labalive/experiment/lti/ • https://en.wikipedia.org/wiki/Low-pass_filter • https://nptel.ac.in/courses/117101055/group10/grp10/sas_10/pa ge06_8_3_2004.php • https://www.electronicshub.org/active-low-pass-filter/ • https://www.electronics-tutorials.ws/filter/filter_2.html • Images are taken from the above sites
- 9. Thank You !!
Editor's Notes
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