Which type of capacitor are used in RF coupling circuit

Which type of capacitors are used in RF coupling circui

  1. 32) Which type of capacitors are used in RF coupling circuit? A) Tantalum B) Monolithic C) Electrolytic D) Metalized poly propylene Answer is: Monolithi
  2. English, 18.11.2020 18:50, rajveer8591 Which type of capacitor are used in RF coupling circuit
  3. um electrolytic, and alu
  4. The ceramic capacitor is a type of capacitor that is used in many applications from audio to RF. Ceramic Capacitor Values of ceramic capacitor range from a few picofarads to around 0.1 microfarads
  5. RF noise occurring on power lines and power circuits tend to be lower in frequency. Power-line de-coupling capacitors are most commonly either: X capacitors (connected from power line to power line) or. Y capacitors (connected from each power line to ground/earth

Figure 2-15. - Transformer-coupled rf amplifier. In this circuit, the secondary of T1 and capacitor C1 form a tuned circuit which is the input-signal-developing impedance. The primary of T2 and capacitor C2 are a tuned circuit which acts as the output impedance of . Q1. (Both T1 and T2 must be rf transformers in order to operate at rf frequencies. Polyester film capacitors, commonly used for coupling between two circuits. In analog circuits, a coupling capacitor is used to connect two circuits such that only the AC signal from the first circuit can pass through to the next while DC is blocked. This technique helps to isolate the DC bias settings of the two coupled circuits An antenna is a passive component that is used to convert an RF electrical signal into electromagnetic radiation (EMR), or vice versa. With other components and conductors we try to minimize the effects of EMR, and with antennas we try to optimize the generation or reception of EMR with respect to the needs of the application

Which type of capacitor are used in RF coupling circui

As a general guideline, we always recommend adding a single 100nF ceramic capacitor and a larger 0.1-10uF electrolytic capacitor for each integrated circuit on your board. Saving Your Integrated Circuit's Life. There you go, everything you might need to know about what decoupling capacitors are in only 5 minutes in today's Electronic Byte In aluminum electrolytic capacitors, aluminum foil acts as anode insulating an oxide layer which is dielectric and covered by the electrolyte as a cathode. These can be seen in the circuits of power supply for decoupling and switched mode power supply


Capacitor Selection for Coupling and Decoupling

Silver mica capacitors are used for many RF circuits like oscillators and filters. Silver mica gives a very high-level performance with close tolerance values but small change in terms of temperature. It uses silver electrodes that are plated directly onto the mica Typically for decoupling capacitors, ceramic capacitors are the predominant type used. The value of the capacitor is usually between 100nF and 10nF. However, usually 100nF capacitors are used most commonly. So, the most used type of decoupling capacitor is a 100nF ceramic capacitor The main RFID coupling techniques include backscatter, inductive and capacitive coupling. The type of coupling technique that is used will depend upon the particular application, and in turn this affect the choice of frequency band. RFID coupling basics. There are several ways in which the RFID reader-writer can communicate with the RFID tag Dt60 Rf Power Capacitor 12kv 300pf 60kva Coupling Circuits Bypass Capacitor , Find Complete Details about Dt60 Rf Power Capacitor 12kv 300pf 60kva Coupling Circuits Bypass Capacitor,Dt60 Capacitor 12kv,Rf Power Capacitor 300pf,Coupling Circuits Bypass Capacitor 60kva from Supplier or Manufacturer-Cixi Anxon Electronic Co., Ltd DT60 RF power capacitor 12KV 300PF 60KVA Coupling circuits bypass capacitor, US $ 20 - 100 / Piece, CCG81 RF Power plate capacitor, CERAMIC CAPACITOR, China.Source from Cixi Anxon Electronic Co., Ltd. on Alibaba.com

The bypass capacitor is used to push the noise signals whereas the decoupling capacitor is used to smoothen the signal through stabilizing the distorted signal. Thus, this is all about an overview of filter capacitor, working, formula, circuits, and its applications. Here is a question for you, what is the main function of a filter capacitor A ceramic capacitor is considered to be one of the most commonly used capacitors. The material used in this capacitor type is dielectric. Also, ceramic capacitors are a non-polar device which means that they could be used in any direction in the circuit. Ceramic Capacitor Symbol. Types of Ceramic Capacitors

Capacitor Selection for Coupling and Decoupling Application

220uf 450v 22x40mm radial aluminium electrolytic capacitor

When used in series (left drawing) or parallel (right drawing) with its circuit compliment, an inductor, the inductor-capacitor combination forms a circuit that resonates at a particular frequency that depends on the values of each component. In the series circuit, the impedance to current flow at the resonant frequency is zero with ideal. A MIM capacitor consists of parallel plates formed by two metal planes separated by a thin dielectric [11]. MIM capacitors are used in RF circuits for oscillators, phase-shift networks, coupling, and bypass capacitance. They are also useful for analog design, due to their highly linear nature and dynamic range [5] Selecting a Suitable Capacitor. When selecting ceramic chip capacitors for use in RF wireless applications, it is important to establish overall circuit performance criteria. The component should then be matched to the specific application requirement. A typical shopping list of performance requirements for this circuit element may include the. resonance circuits is the fact, that any narrowbanded resonance circuit may be approximated by the ideal ones around resonance frequencies. This property reduces significantly the efforts that are required to understand and explore operations of tuned bandpass circuits, which are frequently used in RF-communication systems Generally, mica or ceramic capacitors, ranging in value from about 50 μμf. to 0.01 μf., are used for r.f. bypassing arrangements of this type. If the pentode is employed as an audio-frequency amplifier, high-quality paper or electrolytic capacitors are used. Their proper value can be determined in the same way

RF POWER AMPLIFIERS - TANK CIRCUITS & OUTPUT COUPLING by Lloyd Butler VK5BR The output tuning and coupling of the final RF amplifier is an important part of the transmitter. It is designed to load the amplifier for optimum power output with a minimum of harmonic content. Here are a few notes on its design Coupling Circuits and Techniques. To connect analogue circuits together there are three basic methods, Direct Coupling, Capacitive Coupling and transformer coupling. All have different properties and can be used in any linear or non-linear circuit. With direct coupling, or DC coupling, two components are connected directly to each other 51. A type of oscillator wherein the frequency is determined by the charge and discharge of resistor-capacitor networks used in conjunction with amplifiers or similar devices. A. Sine wave oscillator. B. Beta generating circuit. C. Relaxation oscillator. D. Simply an oscillato An electric circuit is said to be a coupled circuit, when there exists a mutual inductance between the coils (or inductors) present in that circuit. Coil is nothing but the series combination of resistor and inductor. In the absence of resistor, coil becomes inductor. Sometimes, the terms coil and inductor are interchangeably used

Transistor Topics, February 1960 Popular Electronics - RF Cafe

Single layer capacitors, aka thin-film caps (TFCs) Single-layer caps are the choice for the highest frequency response. Also called thin-film capacitors, when realized monolithically, they can be used as in microwave circuits well beyond W-band (<110 GHz). TFCs are used in MMICs and RFICs for bypass,DC blocking and RF tuning elements Ceramic capacitors are the most common capacitor type since they are inexpensive, offer a wide range of values, and provide solid performance. Tantalum, OSCO N, and Aluminum Electrolytic capacitors are all polarized (specifically to be used as a bypass capacitor). Tantalum found their niche in low-voltage systems Recently, C. F. Marki, v. D. Kodwani, F. A. Marki have devised a new kind of Magic-T circuit composed of a balun and two parallel coupled transmission lines which has already exceeded octave bandwidth performance using suspended substrate, broadside coupled lines—the balun tends to be the bandwidth limiting element of this coupler But in the real world, capacitors have a small value of finite internal resistance. This resistance comes from the dielectric material, leakage in an insulator or in the separator. Adding to this, Equivalent series resistance or ESR will have different values in different types of capacitors based on its capacitance value and construction Coupling capacitors are used to block D.C. (D.C. = bad Ju-ju) , and pass A.C. (A.C. = the music signal). However, a coupling capacitor acts as a high pass filter, meaning it will attenuate frequencies below a certain point. The point at which the frequency rolloff is down -3db.

Different Types of Capacitors and their Uses

Ceramic capacitors: These are widely used for decoupling or bypassing on a power supply pin of an integrated circuit (IC). They also keep any stray RF signals out of the voltage supply. Electrolytic capacitors: These capacitors are used in circuits and power electronics, where there is high power consumption. Tantalum capacitors: Because of the. Note that a decoupling capacitor is not a specific type of capacitor. In theory, any capacitor could be used for decoupling. Electrolytic capacitors are excellent candidates for use as large decoupling capacitors as they are cheap, available in a wide range, have high capacitance-to-volume ratio, and have a broad range of operating voltages

Practical receiver design (1): battery operated TRFs

The types of capacitors that are commonly used for filtering applications in SMPSs include aluminum electrolytic capacitors, tantalum capacitors, film capacitors, and ceramic capacitors. The type and amount of capacitors to be used for a specific application mainly depend on the operating conditions of the power supply This coupling type is most appropriate for the RF amplifiers as the reason that the size of the transformer can be maintained so small. Capacitor Coupling. This type of coupling method offers electrical separation (which means blockage of DC) between the cascaded stages and permits the AC signals

First of all, we boil it down to two capacitor types: Polarized capacitor. Non-polarized capacitor. The difference between a polarized capacitor and a non-polarized capacitor is that the polarized capacitor has a positive and a negative side. So it must be placed with the positive pin where the most positive voltage is The use of bypass capacitors in Digital circuits with microprocessor and controllers is slightly different. The major function of bypass capacitors in digital circuits is to act as charge reservoirs. In digital circuits, where the logic gates are switched at high frequency, there is requirement for a large current during the switching Inductors and capacitors are the principal components used in RF tuning circuits. The resonant frequency of a tank circuit is the frequency to which the inductor- capacitor combination is tuned and is found from: (4-1) or, if either the inductance (L) or capacitance (C) is known or preselected then the other can be found by solving Eq The most practical methods that can be used for the design of wireless chargers are namely 'Inductive Coupling Type' and 'Magnetic Resonant Induction'. These are the two methods that use the Faradays Law of Electromagnetic Induction as the principle and Magnetic flux as propagating phenomenon to achieve wireless power transmission This is the first article in a three-part FAQ series on capacitors used in power-handling applications. This article will consider safety capacitors for filtering electromagnetic interference (EMI, also called radio frequency interference, RFI) on ac power lines, for antenna coupling, and for providing voltage isolation in DC/DC converters

Thank you for your inquiry about capacitors in the audio path around our SigmaDSP parts. In general, there are 3 types of capacitors that will be available in the values that are appropriate as AC coupling in most signal paths: electrolytic, tantalum and ceramic. Each has strengths and weaknesses Film Capacitor typically denotes polyester or polymer film as the dielectric - as another answer points out, metallized film capacitors are the same thing: A metallic coating being applied to an extremely thin polymer film, to create the conducting electrodes of the capacitor. In general, ceramic capacitors are somewhat non-linear in their frequency and voltage responses, compared to film.

In summary, the best solution to test a capacitor without actually desoldering it is either using an ESR meter or smart tweezers. Both work the same and are fine to use. But the ESR meter is preferred for through-hole capacitors, and the latter one is preferred to test SMD capacitors. In the rest of the article, I give more info on what are the. Mini-Circuits ZCDC20-E18653+ is a coaxial directional coupler with 20 dB nominal coupling across the 18 to 65 GHz frequency range. This model provides RF input power handling up to 12W and passes DC current up to 0.48A. Figure 3: Performance curves for Mini-Circuits' ZCDC20- E18653+ The coupling-capacitor device uses as a voltage divider a coupling capacitor consisting of a stack of series-connected capacitor units, and an auxiliary capacitor, as shown schematically in Fig. 1. The bushing device uses the capacitance coupling of a specially constructed bushing of a circuit breaker or power transformer, as shown. There are only three basic components in any electronic circuit design- resistor, capacitor, and inductor. We have already covered the introduction to a resistor and its different types, and also covered capacitors and its different configurations.In this tutorial, we are going to know about different types of inductors and how to choose an inductor for different applications

Capacitive coupling can exist between two electrically conductive materials separated by a dielectric medium capable of storing charges. For the pipeline on the ground, capacitive coupling could exist between HVAC transmission line and pipeline. However, when the pipeline is buried in soil, there is no such kind of AC interference They are widely used as filters in low-voltage power supplies and as coupling devices in audio and RF stages. An aluminum electrolytic capacitor consists of two aluminum foil plates separated by a porous strip of paper (or other material) soaked with a conductive electrolyte solution. Construction of a typical device is illustrated in Figure 5.6 Li ion capacitor is the common example of this type. The following figure shows different types of Hybrid Capacitors. They have high tolerance in a wide range of temperature variations from -55°C to 200°C. Hybrid capacitors are also used in airborne applications. Though cost is high, these capacitors are highly reliable and compact Capacitors used in noise-filtering applications can be broken down into three main types, according to the material used for the dielectric: Ceramic: characterized by long life and high voltage, but low capacitance. These are an often-used all-around choice. Plastic film: a thin sheet of plastic for the dielectric may be composed of any number. The capacitor is a two terminal electrical device used to store electrical energy in the form of electric field between the two plates. It is also known as a condenser and the SI unit of its capacitance measure is Farad F, where Farad is a large unit of capacitance, so they are using microfarads (µF) or nanofarads (nF) nowadays

A low value coupling capacitor with the MIC sufficient to handle the capacitive reactance of the MIC which may be around 4k at 3kHz. A 1u coupler is included between the oscillator and the audio amplifier in order to make up for the low impedance rendered by the 47k base resistor The frequency response of this amplifier is the most important factor. The circuit designs of low frequency and audio transistor circuits are different from RF applications. The capacitors and the type of FET used in the operation may affect the frequency response of the amplifier. The frequency response of this amplifier is limited


So now we can finally pick a capacitor value. The rolloff frequency of a R-C filter is. F = 1 / (2 π R C) When R is in Ohms, C in Farads, then F is in Hertz. The final audio amplifier circuit is therefore: C1 attenuates components of the input signal from about 20 Hz down, and completely blocks DC The wave trap connected in series with the feeder line is a kind of reactor. This reactor along with the Coupling Capacitor of the line creates a filter circuit to block the frequencies other than power frequency. This type of reactor is mainly used to facilitate Power Line Carrier Communication. This is called Tuning Reactor Here, you should use—at least—a 6 nF capacitor to compensate a 0.5 V maximum voltage within 6 ns. Note that some guidelines would recommend using two 3 nF capacitors in parallel in this example as this would reduce ESR by a factor of 2, but this will also reduce ESL by a factor of 2, so the effect on damping is nil The above is an example of a general circuit for an AC/DC converter and a DC/DC converter. (1) Safety Certified capacitors are required for AC line filters (C1, C2) and coupling capacitors (C3) in primary and secondary coupling The normal types of capacitors we use on PCB's are largely not usable here due to problems like (a) volrage tolerance, (b) Quality factor, high frequency characteristics in particular, (c) heat dispersal and (d) capacitance value stability, etc., etc. Air variable capacitor The most conventional type of variable capacitor, but big and bulky

The capacitor CB is called blocking capacitor it further blocks the D.C current from reaching to the base. The resistors R1, R2 and RE are used to provide D.C bias to the transistor. Colpitts Oscillator. The colpitts oscillator is widely used in commercial signal generators from frequencies between 1 MHz and 500 MHz A Resistance Capacitance (RC) Coupled Amplifier is basically a multi-stage amplifier circuit extensively used in electronic circuits. Here the individual stages of the amplifier are connected together using a resistor - capacitor combination due to which it bears its name as RC Coupled. Figure 1 shows such a two-stage amplifier whose. Filter circuits are used to remove unwanted or undesired components from a signal. When coupling more than one signal or band to/from an antenna, networks that filter and match impedances such as Pi filters and T filters are bridges in that last connection from the RF transceiver to the antenna Filter capacitors. Capacitors are reactive elements, which make them suitable for use in analog electronic filters. The reason for this is that the impedance of a capacitor is a function of frequency, as explained in the article about impedance and reactance.This means that the effect of a capacitor on a signal is frequency-dependent, a property that is extensively used in filter design

Decoupling Capacitors & RF Networks EMC Bayswater Pty Lt

Suitable for high-voltage applications, RF capacitors are available from AVX, Cornell Dubilier and Johanson Manufacturing Corp at Future Electronics. Our range of RF microwave capacitors are used in RF amplifiers, LC filters and networks, power amplifiers, cordless and cell phones, laser devices and more AVX Thin-Film Directional Couplers are offered in a variety of frequency bands compatible with various types of high frequency wireless systems. Thin-Film Directional Couplers from AVX come in three miniature sizes (0402, 0603, and 0805), offering high directivity, low insertion loss, high isolation, tape and reel, and are surface mountable There are two types of non-radiative wireless power transfer systems, namely, the magnetic field coupling type and the electrical field coupling type. Of these, the magnetic field coupling type of electromagnetic induction method of wireless power transfer has been widely used since the 1990s to charge the battery of cordless telephones. In RF circuits, above about 14-18KHz, the impedance of a Metal Film resistor changes - see the attached diagram. So you have to be sure about the resistor value and frequency in RF circuits. In Audio Frequency circuits, generally no problem, because the audio signal ceases at about 15KHz

This tutorial is a practical guide to selecting the right capacitor for any circuit. Capacitors are available in sizes from 1pF (1 x10 -12 F) to 100,000mF. Depending on the type of capacitor, it may not be available in every value. The general rule is always use a capacitor with a higher working voltage than the circuit it is used in However, the Q factor is one of the most important capacitor characteristics in the design of RF circuits. At RF frequencies, the ESR increases with frequency due to the skin effect. Along with the increase in ESR, dissipative losses increase as well. This is why RF circuits typically use high-Q capacitors to reduce high-frequency losses

RF amplifier coupling - tpub

When the capacitors are used in tone control or tone correction circuits the value is more critical and it is worth using replacements that are closer in value. Some restorers like to fit the modern replacement capacitor inside the case of the old one, which leaves the underside of the chassis looking original The coupling capacitor CG blocks the high DC voltage at the plate of the driving tube while allowing audio signals to pass. Unless bass attenuation is desired, the capacitor needs to be large enough to induce very little signal attenuation at bass frequencies. (82Hz is the lowest note on a guitar with standard tuning. A capacitor is an electrical device for storing charge. In general, capacitors are made from two or more plates of conducting material separated by a layer or layers of insulators. The capacitor can store energy to be returned to a circuit as needed. The capacitance (C) is defined as the ratio of the stored charge (Q) to the potential. Mica capacitors are the stable, reliable and high precision capacitors. These capacitors are available from low voltages to high voltages. The capacitance values of the mica capacitors ranging from 20 pF to 10 µF. Mica capacitors are mostly used in the applications where high accuracy and low capacitance change over the time is desired The best capacitor types for audio circuits are polystyrene and polypropylene. Polystyrene is the first choice, but are only available in values up to .001 uF. Above that value, polypropylene is the type of choice, with nearly the same qualities of dissipation factor (DF) and dielectric absorption (DA) as polystyrene (these are the two.

Capacitive coupling - Wikipedi

Ceramic Capacitors The most commonly used and produced capacitor The name comes from the material from which their dielectric is made. Small size both physically and capacitance-wise. Don't normally go up to 10µF even. Has lower ESR and leakage currents than electrolytic caps. Cheapest type Multiple ceramic single layer capacitors can be used to increase the level of capacitance if this is required in a particular application. Ceramic single layer capacitors are often used for temperature compensation, coupling and decoupling, resonant circuit, bypassing, AC power supply and filter applications. Types of ceramic single layer. with capacitive coupling if high voltages are applied at the ends of the antenna, and standing-wave effects can cause nonuniformity if the coil length is an appreciable fraction of the rf wavelength. These problems can be engineered away, and the TCP has been a very successful ICP

Device dimensions used in ESD-detection circuits for HSPICE simulation. Type R 1 C 1 M P3 (W/L) M N3 (W/L) With ideal capacitor 100 kX 2pF 100 lm 0:15 lm 20 0:15 lm With NMOS capacitor 100 kX 2pF 29 lm 28 lm 100 m 0:15 l m 20 0:15 l Fig. 4. Schematic of MIM capacitor. Fig. 5. Schematic of MOM capacitor. Fig. 6. MOM capacitor structure used in. For both input and output use use connectors isolated from the enclosure, but connect the connector ground terminal through a capacitor (1. 10 nF) with as short wire as possible. The capacitor will have a low impedance at RF, but 100 k. 1Mohm impedance at hum frequencies and their harmonics, thus adding very little hum

Coupling capacitors, on the other hand, provide DC isolation while creating an intentional path for audio, video, RF, and high-speed digital data. Coupling capacitors are often found on high speed interfaces to ensure that any DC potential difference on connected devices does not manifest as ground currents between the devices The normal types of capacitors we use on PCB's are largely not usable here due to problems like (a) volrage tolerance, (b) Quality factor, high frequency characteristics in particular, (c) heat dispersal and (d) capacitance value stability, etc., etc. Air variable capacitor The most conventional type of variable capacitor, but big and bulky A novel high performance transconductor-based mutually coupled circuit topology is presented, employing four active devices (six, if differential-output devices are not available) and only grounded passive elements. The primary and secondary self-inductances and the mutual inductance can be controlled independently. Being constructed with integrator and transconductor blocks, the circuit.

How to Select R

Passive Components in RF Circuits Introduction to RF

This dielectric material is how we specify the capacitor type, e.g., mylar, polypropylene, electrolytic, ceramic, etc. With Dielectric Absorption (DA) even after the initial voltage gets removed from the capacitor terminals by shorting out the capacitor, the capacitor returns to its prior state of charge without any signal being supplied In the area of factory automation (FA *1), the smart factory trend has led to a heightened need for smaller devices, improved reliability and higher heat resistance.While in the area of ceramic capacitors, the commercialization of products that are compatible with a wider capacitance range and that support higher withstanding voltage specifications is being promoted

What Are Decoupling Capacitors in 5 Minutes EAGLE Blo

thus improvising an RF choke, he concluded that the means of coupling was via the microphone cable. Several facts suggested that improper circuit ground-ing might be a large part of the problem. First, Muncy's classic 1994 paper [1] highlighted improper grounding techniques that caused common impedance coupling, which he called the pin 1 problem The power received by the body coupling (using the 3M Red Dot Ag/AgCl 2237 wet electrode) is 30-70 dB higher compared to RF transmission at 2.4 GHz on and around the body, and up to 50 dB higher. So the X rated capacitor checks and reduces symmetrical interference. In Capacitor Power Supplies it is connected in series with the line (line to line connection) to drop voltage. In radios, televisions and other electronic devices these type of capacitors are used to filter Electrical Noise

The amplified signal appears on the plate circuit where it is passed on to the audio output stage through coupling capacitor C-32. Developt the AVC (automatic volume control) voltage - A negative voltage is developed across the volume control R-27 as a result of the rectification of the signal by the diode section (pins 4 &5) A capacitor that serves to block DC voltage from AC voltage is known as a coupling capacitor. Microphones also use coupling capacitors to block DC signals from the signal that is being recorded. While the DC signal is needed to power the microphone, only the AC signal is required in the finished audio recording The best inductor to use is a foil-wound type, which will offer a low series resistance as well as superior inductive properties. Differences in audio capacitors. Capacitors are the focus of this technical bulletin. There are four basic types of capacitors: electrolytic, ceramic, metallized film and film and foil. Electrolytic capacitors

Types of Capacitor and their Applications - Codrey Electronic

The circuit diagram of a typical Colpitts oscillator using transistor is shown in the figure below. In the circuit diagram resistors R1 and R2 gives a voltage divider biasing to the transistor. Resistor R4 limits the collector current of the transistor. Cin is the input DC decoupling capacitor while Cout is the output decoupling capacitor This document and its contents are the property of Mini-Circuits. Sht. 5 of 15 Figure 3 Typical Frequency Response of an RF Transformer A further influence on transformer insertion loss is high AC or DC current. Most RF transformers are used in small-signal applications, in which typically up to 250 mW of RF o

Wideband DTV UHF Antenna TV Amplifier Circuit - 2sc3358

EMI Shielding and Filtering. Shielding is a technique used to control EMI by blocking the transmission of radio frequency (RF) noise from a source, comparable to how lead and concrete are used as a shield from nuclear radiation. Shields can be deployed within the circuit at the RF source, the receiver or anywhere in between The radiation-pressure coupling between two harmonic oscillators has been used in optomechanics for breakthrough experiments in the control and detection of mechanical displacement. Used primarily. Figure 3: Mechanical stress on the PCB is coupled to the dielectric through the capacitor end caps Piezoelectricity can be a major problem for electronics installed in high-vibration environments. In such applications the need for high capacitance, low ESR and ESL, and small size may lead an engineer to select a high-k ceramic capacitor (X7R. The gain of the circuit can be set from the R6/R5. For capacitor C3 to improve a high-frequency response better. Resistor-R9 bring a supply voltage and limit the current to connected to the circuit when the circuit for the condenser microphone. If you do not use it can remove R9 away. Cassette Preamplifier circuit using a BC109 transisto Table 2 lists the type and origin of potential noise sources in cables. Twisted-pair lines intercept coupled signals equally, so the incident signals appear only as common-mode signals. Twisted-pair lines are said to be balanced if the impedances connected from each line to the local common are identical