Filter. Vіdsіkayuchi zayve. Magazine "Autosound". Filters on OU microcircuits

» - May be affected by the active low-pass filter. Vіn especially korisny with an expanded stereophonic sound system on an additional speaker, which only works at the lowest frequencies. This project is composed of an active filter of a different order with a regulated cutoff frequency of 50 - 250 Hz, an input booster with a power adjustment (0.5 - 1.5) and an output cascade.

The design is secure with a direct connection to the switch with a broken circuit, so that the failure signals are visible one by one in phase by 180 degrees. Zavdyaki vbudovanuyu dzherel zhivlennya, stabilizer on the board, you can ensure the zhivlennya filter symmetrical naprugo vіd pіdsiluvаchі natuzhnostі - as a rule, the bipolar 20 - 70 V. Filter LF is ideal for sleeping robots with industrial and self-contained tadsilyuva

Principle diagram of LPF

The filter circuit for the subwoofer is shown as a small picture. Pratsiuє on the basis of two operational subsidiaries U1-U2 (NE5532). The first one is responsible for summing up and filtering the signal, while the other one ensures the same cashing.

Schematic diagram of low-pass filter to subwoofer

The stereo input signal is fed to the GP1 socket, and then through the capacitors C1 (470nF) and C2 (470nF), the resistor R3 (100k) and R4 (100k) is fed to the inverting input of the power supply unit U1A. On this element of implementation, the adder signal with the regulation of the coefficient of reinforcement, selection for the classical scheme. Resistor R6 (27k) together from P1 (50k) allows you to adjust the power in the range of 0.5 to 1.5, which allows you to adjust the power of the subwoofer as a whole.

Resistor R9 (100k) improves the stability of the U1A robot and ensures good polarization at different input signal levels.

The signal from the output of the switch is sent to the active low-pass filter of a different order, prompting to U1B. This is the typical Sallen-Key architecture, which allows you to select filters with different steepness and amplitude. Capacitors C8 (22nF), C9 (22nF) and resistors R10 (22k), R13 (22k) and potentiometer P2 (100k) are directly poured onto the shape of the characteristics. The logarithmic scale of the potentiometer allows you to reach the linear change of the boundary frequency for the hour of wrapping the handle. A wide range of frequencies (up to 260 Hz) can be reached with the extreme left position of the potentiometer P2, turning to the right, making a sound of a range of frequencies up to 50 Hz. The small scale shows the amplitude characteristic of the entire circuit for the two extreme and middle positions of the potentiometer P2. In the case of a skin tone, the potentiometer P1 is set to the middle position, which ensures the strength of 1 (0 dB).

The signal from the output of the filter is processed for the help of the substation U2. Elements C16 (10pF) and R17 (56k) ensure stable operation of m/s U2A. Resistors R15-R16 (56k) increase the strength of U2B, and C15 (10pF) increase its stability. On both outputs of the circuit, there are filters that are added to the elements R18-R19 (100 Ohm), C17-C18 (10uF / 50V) and R20-R21 (100k), through which signals go to the output socket of GP3. The beginning of such a design, at the output we take two signals that are out of phase by 180 degrees, which allows you to directly connect two power supplies and a power supply with a broken circuit.

The filter has a simple block of life with a bipolar voltage, based on zener diodes D1 (BZX55-C16V), D2 (BZX55-C16V) and two transistors T1 (BD140) and T2 (BD139). Resistors R2 (4.7k) and R8 (4.7k) are an intermediate struma of stabilitrons, and were chosen in such a way that at a minimum voltage the strum would add up to 1 mA, and at a maximum it would be safe for D1 and D2.

Elements R5 (510 Ohm), C4 (47uF / 25V), R7 (510 Ohm), C6 (47uF / 25V) - simple voltage smoothing filters on the T1 and T2 bases. Resistors R1 (10 ohms), R11 (10 ohms) and capacitors C3 (100uF / 25V), C7 (100uF / 25V) are also a life voltage filter. Rose of life - GP2.

Subwoofer filter connection

Warto means that the filter module for the subwoofer is to blame but before the output of the front switch after the loudness control, in order to improve the loudness control of the system. The power adjustment potentiometer can be adjusted to adjust the loudness of the subwoofer to the loudness of the entire signal path. Prior to the output of the module, it is necessary to connect whether there is any pressure relief device, which works in the classical configuration. For consumption, vikoristovyte only one of the output signals, broken in phase by 180 degrees, one of one. Offending the exit signals can be beaten up, as it is necessary to call the bridge at the bridge configuration.

Psychoacoustics (science, which makes the sound of yoga pouring into a person) has established that the human ear can perceive sounds in the range of 16 to 20,000 Hz. The one that has a range of 16-20 Hz (low frequencies) is received not by the ear itself, but by the dotik's organs.

A lot of music lovers are stuck with it, that most of the acoustic systems that are supplied are not satisfied with their needs in the world. Zavzhdy є drіbnі shortcomings, nepriemnі nuances thinly, yakі sponkayut pick up columns with podsiluvachami with their own hands.

There may be other reasons for folding the subwoofer (professional interest, hobby).

Subwoofer (subwoofer) is a low-frequency speaker that can produce sound in the range of 5-200 Hz (depending on the design type and model). It can either be passive (wicorist output signal of a near-silencer) or active (equipped with a booster-signal).

Low frequencies (bass) can be divided into three main types:

• Upper (Eng. UpperBass) - from 80 to 150-200 Hz.
• Middle (English MidBass / midbass) - like 40 to 80 Hz.
• Deep or deep bass (English SubBass) - everything is lower than 40 Hz.

Frequency filters are set for both active subwoofers and passive subwoofers.

The advantages of active low-frequency speakers in the offensive:

• The active subwoofer subwoofer doesn't add to the acoustic system (so how to live well).
• The input signal can be filtered (third-party noise is switched on from the high frequencies, the robot will be more concentrated on that range, in which the speaker will ensure the highest transmission clarity).
• Pіdsilyuvach with the right approach to the design, you can gnuchko nalashtovuvatsya.
• The external spectrum of frequencies can be divided into a few channels, with which you can also work with okremo - low frequencies (on a subwoofer), mid, high, and sometimes overhead frequencies.

See filters for low frequencies (LF)

For implementation

• Analog circuits.
• Digital extensions.
• Software filters

Type

• Active filter for subwoofer(so the titles of the crossover, obov'yazykovy attribute of any active filter - dodatkovo dzherelo zhivlennya)
• Passive filter (such a filter for a passive subwoofer does not absorb the required low parts in a given range, without overpowering the signal).

For steep decline

• First order (6 dB/octave)
• Other order (12 dB/oct.)
• Third order (18 dB/octave)
• Fourth order (24 dB/octave)

Main characteristics of filters:

• Smuga bandwidth (range of frequencies that are skipped).
• Smuga zatrimuvannya (range of suffocation signal).
• The frequency of sight (the transition between smogs of transmission and trimming is considered non-linear. The frequency, for which signal is passed, is attenuated by 3 dB, is called the frequency of sight).

Additional parameters for assessing acoustic signal filters:

• The steepness of the decline ACH (Amplitude-frequency characteristic of the signal).
• Irregularity in the smoothness of the transmission.
• resonant frequency.
• Goodness.

Linear filters of electronic signals are divided among themselves into square curves (deposit of indications) of frequency response.

Variations of such filters are most often referred to as the names of the scientists, as they revealed the following patterns:

• Butterworth filter (smooth frequency response for smooth transmission),
• Bessel filter (characteristic of a smooth group fade),
• Chebishev filter (steep drop in frequency response),
• Elliptical filter (frequency response pulsations in swags are passed and strangled),

That іnshi.

The simplest low-pass filter for a subwoofer in a different order, it looks like this: the inductance (coil) is connected in series to the speaker and in parallel - the capacitance (capacitor). The following are the ranks of the LC filter (L is the designation of inductance on electrical circuits, and C is the capacitance).

The principle of robotic action in the offensive:

1. Opir inductance is directly proportional to the frequency and to that the coil passes low frequencies and cuts high (the higher the frequency, the higher the opir inductance).
2. The volume control is wrapped in proportion to the frequency of the signal and that the high-frequency noise is turned off at the input of the speaker.

This type of filters is passive. More folding in the implementation - active filters.

How to make a simple filter for a subwoofer with your own hands

As it was said more, the simplest thing about the design is passive filters. The stench may be at the warehouse less than a few elements (a little to deposit in the necessary order of the filter).

You can choose your own low-frequency filter for ready-made circuits in the measure, or for individual parameters after detailed design of the necessary characteristics (for clarity, you can know special calculators for filters of different orders, for the help of which you can quickly design the parameters of storage elements, etc.). ).

For active filters (crossovers), you can use special software, for example, such as Crossover Elements Calculator.

In some cases, when designing a circuit, a filter summator may be needed.

Here, offending the sound channels (stereo), for example, after the output from the subwoofer, etc., it is necessary to filter out a little (leave out only a few low frequencies), and then combine them into one for an additional adder (the subwoofer is often installed only one). Abo navpaki, pochatku pіdsumovuvati, and then filtruvati woofer.

As a butt, take the simplest passive low-frequency filter of a different order.

If the speaker is 4 ohms, the frequency is transmitted - 150 Hz, then the type of filtering according to Butterworth will be needed.

Goodbye, dear readers! Today's mova pide about choosing a simple low-pass filter. Ale, regardless of its simplicity, for the quality of the filter does not compromise store counterparts. Otche, let's do it!

Main characteristics of the filter

• The frequency is 300 Hz, other frequencies are viable;
• Life pressure 9-30 Volts;
• The filter is 7 mA.

Scheme

• DD1-BA4558;
• VD1 - D814B;
• C1, C2 - 10 uF;
• C3 - 0.033 uF;
• C4 - 220 nf;
• C5 - 100 nF;
• C6 - 100 uF;
• C7 - 10 uF;
• C8 - 100 nF;
• R1, R2 - 15 kOhm;
• R3, R4 - 100 kOhm;
• R5 - 47 kOhm;
• R6, R7 - 10 kOhm;
• R8 - 1 kOhm;
• R9 - 100 kOhm - change;
• R10 - 100 kOhm;
• R11 - 2 rooms

Preparing the low pass filter

(advantage: 420)

Practical design of filters for upper and lower frequencies (RC and LC filters)

Good day, radio amateurs!
Today, on the site, on the black one, we can look at you the order of rozrahunku filters of upper and lower frequencies.
For the sake of statistics, you know that you can filter not only the "bazaar", but a lot more. And having learned the article, learn to independently carry out the necessary repairs, as if they will help you with the design or adjustment of various equipment (the article has a lot of formulas, but it’s not scary, really everything is simpler).

We are significant in front of you, you understand "upper" and "lower" frequencies are brought to sound engineering, but understand "high" and "low" frequencies - up to radio engineering.

High Pass Filters (far HPF) that filterslower frequencies (far LPF) zastosovuyutsya in rich electrical circuits and serve for various purposes. One of the yaskravih butts of their zastosuvannya is the color-musical annex. For example, if you type “simple music of colors” in the search system, then remember that the results of the search often show the simplest music of color on one transistor. Naturally, it is important to call such a construction a musical color. Knowing that such filters of the upper and lower frequencies and how the stench is broken, you yourself, independently, can remake such a scheme for a greater total color of musical additions. The simplest way: you take two of the same schemes, but put a filter in front of the skin. In front of one low-pass transistor, and in front of the other - high-pass filter, and you already have a two-channel color music. And if you think about it, you can take one transistor and set two filters (low filter and high filter or one middle frequency) and take the third channel - the middle frequency.

First, continue below about the filters, highlighting their important characteristics. frequency response (frequency response). What a display.

filter frequency response shows how the amplitude of the signal changes, which should pass through this filter depending on the frequency of the signal.
So, at the same frequency, the signal that enters the filter, the amplitude of the amplitude is the same as at the output, and for a different frequency, the filter, pushing against the signal, attenuates the amplitude of the input signal.

Again, there is one more sign: frequency at a glance.

Frequency at a glance – tse frequency, there is a decrease in the amplitude of the output signal to a value equal to 0.7 per input.
For example, even if the frequency of the input signal is 1 kHz with an amplitude of 1 volt at the output of the filter, the amplitude of the input signal changes to 0.7 volts, the frequency of 1 kHz is the frequency of the given filter.

І the rest of the appointment - filter frequency response steepness .

High and low pass filters – ce simple electric lances, so from one chi many elements, like a non-linear frequency response, that is. scho mayut different opir at different frequencies.

Under the summation of the above words, it is possible to make a non-trivial visnovka, which is equal to the sound signal with filters and strong supports, about those only a sign that the opir changes regularly in the frequency of the sound signal. Such an opir is calledreactivei signify yakX.

Frequency filters are made from elements that can reactive support - capacitors and inductance coil . Razrahuvati capacitor reactive support you can follow the formula below:

Xc=1/2pFC de:
Xs- Reactive capacitor support;
P- Vono i in Africa "pi";
F- Frequency;
Z- Condenser location.
Tobto, knowing the capacitance of the capacitor and the frequency of the signal, you can determine which way to repair the capacitor for a particular frequency.

BUT reactive opir of inductance coil axis tsієyu formula:

X L \u003d 2pFL de:
X L- Reactive opir of the inductance coil;
P- Vono i in Russia "pi";
F- signal frequency;
L- Coil inductance

Frequency filters are available for different types:
– one-element;
– G-like;
– T - figurative;
– P - figurative;
– bagatolan.

In this article, we do not omit it deeply into theory, but only look at the surface power, and only the filters that are formed from the supports and capacitors (filters with inductance coils will not be removed).

single element filter

- filter that consists of one element : or capacitor(For viewing high frequencies), or inductance coils (For viewing low frequencies).

G - similar filter

L-similar filter - the most significant voltage dilator with a non-linear frequency response and її can be seen from two supports:

For the help of the voltage dilnik, we can reduce the input voltage to the required level.
Formulas for the calculation of the parameters of the voltage dilator:

Uin = Uin * (R1 + R2) / R2
Uin = Uin * R2 / (R1 + R2)
Rzag=R1+R2
R1=Uin*R2/Uout – R2
R2=Uout*Rzag/Uin

For example, we are given:
Rtot=10 room,Uin = 10 V, at the exit of the dilnika, you need to take Uout = 7 V
The order of the rozrahunka:
1. Significantly R2 \u003d 7 * 10000 / 10 \u003d 7000 \u003d 7 com
2. Significantly R1 \u003d 10 * 7000 / 7-7000 \u003d 3000 \u003d 3 kOhm, or R1=Rzag-R2=10-7= 3 kOhm
3. Revisited Uout = 10 * 7000 / (3000 +7000) = 7 V
What do we need.
Knowing these formulas is necessary not only for inducing a voltage dilator with the necessary output voltage, but also for expanding the filters of lower and upper frequencies, for which you switch lower.

IMPORTANT!
The shards of the opir of the vanity, which are connected before the exit of the dilnika, are added to the vacant voltage, then the value of R2 may be 100 times less for the opir of the opir of the vanity. Although high precision is not required, the value can be reduced up to 10 times.
This is also true when the filters are being rolled up.

To remove the filter from the voltage dilnik on two resistors capacitor.
As you already know capacitor may jet support. In tsimu yogo, the reactive opir at high frequencies is minimal, while at low frequencies it is maximum.

When replacing support R1 on the capacitor (with cioma at high frequencies, the strum passes through the new one without jumping, and at low frequencies, the strum does not pass through the new one) mi matimemo high pass filter.
And when replacing the capacitor support R2 (with this, we use a small reactive support at high frequencies, the capacitor shunts the high frequency jet to the ground, and at low frequencies it is great and the jet does not pass through it) - low pass filter.

As I already said, shanovni radioamatori, we are not deeply familiar with the net of electrical engineering, otherwise we are confused and forgotten about what happened. Therefore, at once we abstract from the complex interrelationships in the world of electrical engineering and look at the topic like a lot of fluctuations, without attachments to anything.
Let's continue. Not everything is so bad. Knowing how to use elementary speeches is a great help in radio amateur practice. Well, it’s not rozrahuymo mi like a filter, but rozrahuymo with mercy. Well, it’s okay, I’ll fix the time when I’ll fix it, and we’ll definitely need the ratings of the radio components.

The order of the distribution of the L-like high-pass filter

In aiming the butts of the expansion of the filter parameters, it is based on the fact that we see the main opir of the voltage regulator, but it’s sing-songly correct, with a practical adjustment of the filters, to designate the opir of the resistor R2 of the dilnik, the value of which may be 100 times less before switching on the voltage. And also, do not forget that the dilnik of the voltage is also squandering the strum, so in the end, it will be necessary to measure the tension, which rises, on the resistors for their correct choice.

Butt: We need to develop an L-like high-frequency filter with a frequency of 2 kHz.

Given: Rzag = 5 com, the frequency of the filter is 2 kHz.
(you can take a specific voltage, but in our case, it does not play any role).
We carry out a rally:
R1 Xc = R1.
R2:

R1:



Xc=1/2pFC=R1 —> C=1/2pFR1:
C \u003d 1 / 2pFR1 \u003d 1/2 * 3.14 * 2000 * 1500 \u003d 5.3 * 10 -8 \u003d 0.053 uF.
C=1.16/R2nF.
6. We recheck the frequency at a glance Fav
Fср=1/2пR1C= 1/2*3.14*1500*0.000000053 = 2003 Hz.
In this rank, we have appointed, that for inducing a high-frequency filter from the given parameters (Rtotal = 5 kOhm, Fav = 2000 Hz) R2 = 3.5 room capacitor Z \u003d 0.053 microfarads.
? For proof:
? 1 uF = 10 -6 F = 0.000 001 F
? 0.1 uF = 10 -7 F = 0.000 000 1 F
? 0.01 uF = 10 -8 F = 0.000 000 01 F
and so far...

The order of the distribution of the L-like low-pass filter

Butt: We need to develop an L-like low-frequency filter with a frequency of 2 kHz.

Given: hot opir of the voltage dilator Rzag = 5 com, the frequency of the filter is 2 kHz.
The input voltage is taken as 1, and the output voltage as 0.7(like i have a frontal vipad).
We carry out a rally:
1. We connected a capacitor instead of a resistor R2, then the reactive opir of the capacitor Xc = R2.
2. It is dependent on the formula of the dilnik of the voltage opir R2:
R2 = Uin * Rtot / Uin = 0.7 * 5000/1 = 3500 = 3.5 kOhm.
3. Variable resistor opir R1:
R1 = Rgen-R2 = 5 - 3.5 = 1.5 com.
4. We check the value of the output voltage at the filter output when the supports are opened:
Uout \u003d Uin * R2 / (R1 + R2) \u003d 1 * 3500 / (1500 + 3500) \u003d 0.7.
5. The capacitance of the capacitor is determined, as it can be deduced from the formula: Xc=1/2pFC=R2 —> C=1/2pFR2:
C \u003d 1 / 2pFR2 \u003d 1/2 * 3.14 * 2000 * 3500 \u003d 2.3 * 10 -8 \u003d 0.023 uF.
Capacitor capacitance can also be calculated using the following formula: C=1/4.66*R2pF.
6. We recheck the frequency at a glance Fav behind the formula, as it is also shown from the pointer:
Fср=1/2пR2C= 1/2*3.14*3500*0.000000023 = 1978 Hz.
In this rank, we have appointed, that for inducing a low-frequency filter from the given parameters (Rtotal = 5 kOhm, Fav = 2000 Hz) it is necessary to stop the opir R1 = 1.5 room capacitor Z \u003d 0.023 microfarads.

T - similar filter

T-shaped filters for high and low frequencies , tse tі f L-similar filters to which one more element is added. In such a rank, the stench is roaring like a voltage diler, which is composed of two elements with a non-linear frequency response. And then, before the rozrahunk value, the value of the reactive support of the third element is subsumed. The second, less accurate way to expand the T-like filter is based on the expansion of the L-like filter, after which the value of the “first” expanded element of the L-like filter is increased, or it changes into two - “divided T-subdividing” into two. If it’s a capacitor, then the value of the capacitance of the capacitors in the T-filter will change twice, and if it’s a resistor or a choke, then a support, otherwise the inductance of the coils will change twice:

P - similar filter

P-similar filters , tse tі f L-similar filters to which one more element is added in front of the filter. Everything that was written for T-like filters is true for P-like ones.
Likewise, in the case with T-like filters, for the expansion of the P-like vicarious formula, the voltage dilator formula is added, with the additional support of the shunting first filter element. The second, less accurate way of expanding the L-like filter starts from the expanding of the L-like filter, after which the meaning of the “remaining” element of the checked element of the L-like filter is changed into two In contrast to the T-like filter, if it is a capacitor, then the value of the capacitance of the capacitors in the P-filter changes twice, and if there is a resistor or a choke, then the value of the support, otherwise the inductance of the coil will increase twice.

As a rule, one-element filters are stuck in acoustic systems. The high pass filters sound T-like, and the low pass filters P-like. The mid-frequency filters, as a rule, are shattered with L-like two capacitors.

For the writing of the article, the crime was also scored for materials from the sitewww.meanders.ruthe author and bishop of that one is Oleksandr Melnyk, for which I thank you very much.

An electrical filter is a device for transmitting electrical signals, which transmits streams in the singing frequency region and crosses their passage through the region. In radio engineering and electronics, electrical filters are divided into passive and active. Passive filter circuits should be replaced by passive elements: resistors, capacitors and inductors.

Before circuits of active filters of the crime of designation of elements, such active devices are included, like transistors or integrated microcircuits. How to filter the power of the add-on is determined by its amplitude-frequency characteristic, which is called the fallacy of the gain coefficient of the add-on to the frequency of the signal. In the real area of ​​frequencies, as it is called a smuga transmission or a swarm of transparency, electrical noise is transmitted by the filter from the entrance to the exit mayzhe without weakening. The pose of the woman's prozorost is smoky, or the fading is fading, in the midst of such a frequency warehouse signal is weakened. There is a frequency between a swarthy transparency and a swirling cloud, as it is called a boundary. At the connection, since there is a smooth transition between a swirl of transparency and a swarm of fading, the frequency is important, for which a weakened signal is equal to -3 dB - it is 2 times less for a voltage, lower for a blur of transparency.

Zavzhd tsіkavo otrimati abrupt transition of the amplitude-frequency characteristics between the woman's transparency and the swarm of light. In passive filters, the greater coolness of such a transition is within the reach of the more complicated schemes and the stasis of Bagatolan systems. Folding filters allow for bulky roses and precise alignment. The active filters of the zavdyaks of the whistle-blower zvezku are significantly simpler and cheaper.

It was accepted to add filters for chotiri of the fallow category in order to re-stuff the smog of transparency:
. low pass filters (0 ≤ f ≤ f 0);
. high pass filters (f ≥ f 0);
. smug filters (f 01 ≤ f ≤ f 02);
. filter (0 ≤ f ≤ f 01 and f ≥ f 02).

Here f is the frequency of signals to pass through the filter; f 0 -limit frequency; f 01 - lower limit frequency; f02 - upper limit frequency. In this way, the low-pass filter nponyckaє warehouse signal, the frequency of which is less than the boundary frequency; the high-pass filter passes the warehouse signal, the frequency of which is greater than the boundary frequency; the smug filter passes the warehouse signal, the frequency of which is between the lower limit frequency f 01 and the upper limit frequency f 02; If a notch filter is used, it will attenuate signals whose frequency is between the lower limit f01 and the upper limit f02. Use and fold filters of special recognition, for example, combed parts of the filter, which will win in the color TV box, which will let through rich dark smugs and weaken the intercourse between them.

Electrical filters are widely used in electrical engineering, radio engineering and electronics. So, at the output, the low-frequency filter is vibrated, which allows you to let through only a constant storage of a straightened stream and weaken the passage of pulsations. In radio receivers, smug filters are widely used, which allow you to see the signals received by the antenna in the faceless radio stations, there is only one, the smuga of frequencies of which is seen in the blur of the transparency of the filter.

Another one subdivided all filters into two categories: filters, a circuit for removing inductance coils, that filter without inductance, RC filters or resistor-capacitor filters.

Active resistor-capacitor filters may outperform their passive counterparts, especially at frequencies below 10 kHz. Passive filters for low frequencies due to large inductance coils and high capacity capacitors. That's why the stench looks bulky, expensive, but the characteristics seem to be far from ideal.

Great inductance can be reached for the size of a large number of coils of the coil and the congestion of the ferromagnetic core. Tse allow for the power of pure inductance, since the old wire of the bagatovitkovo coil can be remembered, and the ferromagnetic core is weak to the temperature at the yogo magnetic power. The need for a large capacitance zmushuy zastosovuvat capacitors, which can ruin the stability, for example, electrical. Active filters for a significant world to save the appointments of shortfalls.

Differentiator and integrator circuits, prompted by the operation of the subsidiaries, the simplest active filters. With the choice of elements of the scheme of heavy fallow in frequency, the differentiator becomes a high-frequency filter, and the integrator becomes a low-frequency filter. Further, the stocks of the most folding and most versatile filters will be looked at. A large number of other possible schemes of active filters at once with their detailed mathematical analysis can be found in various assistants and helpers.

Low Pass Filters
By combining the inverting amplifier circuit with the integrator circuit, the first-order low-pass filter circuit is shown in Rice. one.

Rice. one.

Such a filter is an inverting subsilver, which is a constant coefficient of strength in the smoothness of transparency in the form of a constant stream up to the cutoff frequency f 0 . It can be seen that in the midst of a smog of transparency, as long as the capacitor’s oscillatory support is large, the circuit strength coefficient is increased with the strength coefficient of the power supply, which is inverted:

The cutoff frequency of this filter is determined by the elements of the lancet of the whirlpool link, apparently up to the point:

The amplitude-frequency characteristic - the amplitude of the signal amplitude at the output of the add-on at a constant amplitude at the input of the add-on - is presented on fig.2.

Rice. 2

The Smuzі Zgasannya Vishischi the borders of the frequency F 0 Gright Zhimeni is z -izhtensivnistya 20 dB/decades (Abo 6 dB/octave), the ZMEFITENSED KOEFITSINIT PIDSILENNA for 10 times in the 10 -time freight .

Because such a sharpness of the amplitude-frequency characteristic of the smoothing is not enough, it is possible to turn the low-pass filter of a different order, the scheme of which is shown in fig.3.

Rice. Z

The gain coefficient of the low-pass filter of a different order is the same, like that of the first-order filter, in connection with it, the total opir of resistors at the reverse input, like before, is expressed by the values ​​of R1:

The cut-off frequency when vikonannі mind R 1 C 1 \u003d 4R 2 C 2 is also expressed by the colossal formula:

What is the amplitude-frequency characteristic of this filter, presented on Rice. four, it looks like it’s driven by the steepness of the cheek, like becoming 12 dB / octave.

Rice. four

In this way, in the case of a smoother, with an increase in frequency, the double voltage of the signal at the output of the filter changes by a factor of four.

High Pass Filters
The high-pass filter circuit was similarly motivated, as shown in fig.5. Such a filter is an inverting filter with a constant coefficient of increase in the strength of the transparency smuga in the frequency of f0 and more. In the case of transparency, the coefficient of strength of the scheme is the same as in the case of the sublime, which is inverted:

Fig.5. Schematic diagram of an active first-order high-pass filter

The cutoff frequency f 0 at the level of -3 dB is indicated by the input lancet, apparently up to the point:

The steepness of the sickly amplitude-frequency characteristic, which is presented on fig.6 in the region of the cutoff frequency to become 6 dB/octave.

Fig.6. Amplitude-frequency response of the first-order high-pass filter

As for the low pass filters, it is possible to select an active high pass filter of a different order with the method of suffocating the signal in the extinction smoothing. The principle diagram of such a filter is shown in fig.7.

Fig.7. Schematic diagram of an active high-pass filter of a different order

The steepness of the amplitude-frequency characteristic of the high-frequency filter of a different order to the cutoff frequency region becomes 12 dB / octave, and the characteristic itself is shown in small 8.

small 8. Amplitude-frequency characteristic of the high-pass filter of a different order

Strip filters
If you combine an active low-pass filter with an active high-pass filter, then as a result, a dark filter is established, the principle scheme of which is directed to fig.9.

Rice. 9 . Schematic diagram of an active smog filter

Qiu scheme is sometimes called a selective pidsiluvach with an integro-differentiating pivotal link. Similar to subsilyuvachіv, scho mіstat kolivalnі contours, smugovy filter also maє amplitude-frequency characteristic with a pronounced maximum at the singing frequency. It is impossible to name such a resonant frequency, because resonance is less possible in circuits that contain inductance and capacitance. In other vibrations, the frequency of such a maximum is called the frequency of the quasi-resonance. For a smug filter, as you can see, the frequency of the quasi-resonance f0 is determined by the elements of the lancet of the whirlwind:

The amplitude-frequency characteristic of the smug filter is shown in Rice. ten.

Fig.10. Amplitude-frequency characteristic of smug filter

The maximum gain coefficient at the frequency of the quasi-resonance is equal to:

Vidnosna smuha transmission on the river -3 dB:

The principle diagram of another smug filter is pointed at Rice. eleven.

Rice. eleven. Schematic diagram of a smug filter with a sub-filter T-filter

Here is a lance of a negative turning link of inclusions under the T-filter, solutions by resistors R2, R3, R5 and capacitors Cl, C2, C3.

As you see, as you know, think like this:

amplitude-frequency characteristic of the subwave T-filter

moreover, at the frequency of the quasi-resonance, the transmission coefficient of the undercurrent T-filter is zero. Therefore, an active filter with a sub-filter T-filter, we will turn on a negative serum link in the lances, and a dark filter with a maximum amplitude-frequency characteristic at a frequency of quasi-resonance. Three such characteristics are presented on Rice. 12. The characteristics are controlled by different supports of the resistor R4: the lower one is R4 = 100 kΩ, the middle one is R4 = 1 MΩ, the upper one is R4 = ∞.

Rice. 12. Amplitude-frequency characteristic of an active filter with a subtractive T-filter in a lancet-negative coil

Rejection filters
The same undercurrent T-filter can be included not in the negative flow of the serum link, as it was broken when the smug filter was set, but in the flow of the input signal. When an active notch filter is established, the scheme of which is directed to rice, 13.

Fig.13. Schematic diagram of a notch filter with a sub-filter T-filter

When vikonnі kolishnіh minds

the amplitude-frequency characteristic of the active filter, which may have a lower T-filter at the input lance, to eliminate the quasi-resonance, the frequency of which, as before, is determined by formula (8). Ale at the frequency of the quasi-resonance, the coefficient of strength of the active filter is zero. The amplitude-frequency characteristic of the active filter with a sub-filter T-filter at the input port is shown in fig.14.

Rice. fourteen. Amplitude-frequency characteristic of the active filter with a sub-filter T-filter at the input port

Folding filters
Dekіlka active filters can be reversed sequentially to remove the amplitude-frequency characteristic with increased steepness. In addition, sequentially closed sections of simple filters may reduce sensitivity. Tse means that a small change in the value of one of the components of the circuit (the change in the support of the resistor or the capacitance of the capacitor in the norm) leads to a smaller influx on the residual characteristic of the filter, lower in the case of a similar folding filter, which is used on one operational switch.

Rice. fifteen. Schematic diagram of a staged filter

On the Rice. fifteen indications of the filter stages, selections from three operational subsidiaries. The popularity of such filters grew sharply after the appearance of integrated microcircuits for sale, which could cover a small number of operational devices in one case. The advantages of this filter are low sensitivity to the magnitudes of the components and the possibility of removing three inputs: upper frequencies U vyh1, brown U vyh2 and lower frequencies U vyhZ.

Folding filter from p_dsumovuvacha DA1 and two integrators DA2, DA3, yakі z'ednаnі at the look of a closed loop. How the elements of the scheme are chosen clearly to the point

then the cutoff frequency is equal

The outputs of the upper and lower frequencies may have a steepness of the amplitude-frequency characteristic, which is 12 dB / octave, and the dark output may have a triangular characteristic with a maximum at a frequency of f 0 with a quality factor Q, as it is indicated by the resistors of the DA1 strengthening microcircuit.