A filter is a device or process that separates elements or signals in a mixture. There are several types of filters including low pass, high pass, and band pass filters. A low pass filter passes low frequencies and attenuates high frequencies. It consists of an inductor and resistor or resistor and capacitor. High pass filters have the opposite effect, passing high frequencies and attenuating low frequencies using similar components. Band pass filters selectively pass a range of frequencies using various components like inductors, capacitors, crystals, or op-amps. Filters have many applications in electronics, audio/video processing, communications, and other areas.

2. Filter
 A device or process that removes or separates certain elements or substances from a mixture or signal.
 Filters can be used in a variety of contexts, such as in electronics to remove unwanted noise from a
signal.
 In water treatment to remove impurities, and in air conditioning to remove particles from the air.
Pass filter
 Pass filter is a type of filter that allows certain frequencies or signals to pass through while blocking or
attenuating others.
The frequency range that is allowed to pass through is known as the passband.
the frequency range that is blocked or attenuated is known as the stopband.

3. Types
 Low pass filter
 A low pass filter is a type of filter that passes low frequency signals and attenuates (reduces the
amplitude of) higher frequency signals.
 It is commonly used in audio processing to remove unwanted high frequency noise.
 The cutoff frequency of a low pass filter is the frequency at which the filter begins to
attenuate signals.
Inductive model of a first order low pass filter
 An inductive model of a first-order low-pass filter is a circuit that allows low-
frequency signals to pass through while attenuating or blocking high-frequency
signals
 It is typically composed of an inductor (L) and a resistor (R) connected in series.
 fc = 1 / (2 * pi * sqrt (L * R)).

4. Capacitive model of a first order low pass filter
 The capacitive model of a first-order low-pass filter consists of a resistor in
series with a capacitor connected to ground
 fc = 1/(2πRC)
Application of low pass filter
 Audio processing
 Image processing
 Electronic circuit design
 Control systems

5. High pass filter
 A high-pass filter is a type of electronic filter that allows high-frequency signals to pass
through while attenuating (reducing) lower frequency signals
 High-pass filters are commonly used in a wide range of applications
 circuit designs, signal processing audio processing
Inductive model of a first order high pass
filter
 An inductive model of a first-order high-pass filter can be
represented by a single inductor (L) in series with the input
voltage and a capacitor (C) in parallel with the output
voltage
 fc = 1 / (2 * pi * sqrt(L * C))

6. Capacitive model of a first order high pass filter
 The circuit for a first-order high-pass filter using a capacitor and resistor is simple.
 It consists of a resistor and a capacitor connected in series across the input voltage source
 The capacitor is connected in such a way that its positive terminal is connected to the input
voltage
 Its negative terminal is connected to the output. The output is then taken across the resistor
 fc=1/(2piR*C )
Application of high pass filter
 In audio applications
 In image processing
 In electronic circuits

7. Band pass filter
 electronic filter that is designed to pass a range of frequencies, known as the
passband
 It essentially acts as a frequency-selective amplifier
Type of band pass filter
1. LC band pass filter
 These filters are made up of an inductor (L) and a capacitor (C) in series or in
parallel.
 They are typically used in audio applications
2. RC band pass filter
 These filters are made up of a resistor (R) and a capacitor (C) in series or in parallel
 They are typically used in radio frequency (RF) applications

8. 3. Crystal band pass filter
 These filters use a quartz crystal as the resonant element.
 They are extremely stable and precise, and are commonly used in radio communications
 frequency synthesis applications.
4. Active band pass filter
 These filters use an active component,
 such as an operational amplifier (op-amp),
 in addition to passive components (resistors, capacitors, and inductors) to provide
additional gain and greater control over the filter's characteristics.
Application of band pass filter
 Telecommunications
 Audio and Video Processing
 Radio Communications
 Signal Processing