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What is the effect of capacitance in high frequency circuits and how it is getting added?
Wiki User
∙ 16y ago
First, capacitance is the resistance of something to a change in voltage. And capacitance exists anywhere there is a conductor that is insulated from another conductor. With that definition, anything has capacitance. And that's correct. It is also the key to understanding the capacitance in high frequency (radio frequency or RF) circuits. The fact that a circuit had conductive pathways and component leads and such means that there is a lot of little bits of capacitance distributed around the circuit. The capacitance is already there; it isn't "added" later as might be inferred. Normally, this bit of capacitance isn't a problem. But at higher and higher frequencies, it is. Remember that the higher the frequency of an AC signal, the better it goes through a given cap. So at higher and higher frequencies, the distributed capacitance in the circuit "shorts the signal to ground" and takes it out of the circuit. The RF is said to be coupled out of the circuit through the distributed capacitance in that circuit. The higher the frequency a given circuit is asked to deal with, the more signal will be lost to this effect. It's just that simple. Design considerations and proper component selection minimize the distributed capacitance in a circuit.
Wiki User
∙ 16y ago
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How does capacitance cause signal degradation?
A capacitor is composed of two conductors that are separated by an insulator. This is a simple definition, but it says a lot about capacitance, and it says it very well. By this definition, there could be capacitance just about anywhere in a power system or circuit. Yes! There could! And there is! Capacitance offers "resistance" to alternating current (AC) signals called reactance. The higher the frequency, the less reactance there is and the better the signal will be able to pass through the capacitor. In modern electronic equipment, there are lots of circuit pathways and lots of components in the circuits. This leads to a lot of distributed capacitance in the circuit. This distributed capacitance represents a lot of little pathways for signals to "jump gaps" in the circuit. Signals will avoid going through the components and devices and also avoid following all the pathways it is supposed to follow. The signals will be "shorted around" components or "shorted to ground" in other pathways. This combines to effect signal loss or degradation. The higher the frequency of the signal put through a circuit, the more loss there will be to the signal due to distributed capacitance.
How does one reduce stray capacitance?
You can reduce stray capacitance by avoiding having long wires running parallel in circuits. Keep wires as short as possible. Long wires running along each other can exhibit stray capacitance effects. Another way is to cut long leads of components such as capacitors and inductors to make them as short as possible. If best, use SM components, as they have no leads which can cause this stray capacitance effect.
What is meant by stray capacitance?
ANSWER Stray capacitance is the capacitance in a circuit not caused by capacitor components. There is a small capacitive effect, often on the order of a few picofarads, between leads of ICs, traces on a PCB, wires in a cable, the power and ground planes in a PCB, etc. In high-speed circuits, stray capacitance can be enough to completely change the operation of a circuit -- even to the point of keeping it from working as designed. Note that capacitor "components" can include PCB traces specifically designed to act as capacitors.
Does a period effect the frequency of a soundwave?
Period and frequency are 'locked' together, not independent numbers. They're simply the reciprocals of each other.Period = 1 / (frequency).Frequency = 1 / (period).So definitely, if one changes, the other changes. Their product is always [ 1 ].
What is the effect of under sampling in signals and system?
Bad frequency aliasing. See Nyquist criteria.
What is the effect of inductance in high frequency circuits?
Inductive reactance is proportional to frequency... XL = 2 pi f L ... so, the higher the frequency, the higher the reactance. At a sufficiently high frequency, the inductor would appear to be an open circuit. Note, however, that at very high frequencies, parasitic capacitance becomes a factor.
What is the effect of capacitance at high frequencies?
A: Is the same as low frequency except it becomes a predominant factor.
Increasing the capacitance of the coupling capicitor in an RC coupled amplifier has what effect?
the circuit will pass waves of a lower frequency
How does the Switching diode used in television tuning?
A: Those diodes are used as a variable capacitance whereby applying a voltage changes the capacitance which effect the frequency of the tuning circuit
What is the change in current when frequency changes from 8 khz to 400hz?
That depends on the circuit. For a pure resistive circuit (no inductance and capacitance), the frequency will have no effect on the current.
What are the limitations of conventional tubes at microwave frequency?
2-3Figure 2-1B.-Interelectrode capacitance in a vacuum tube. 100 MEGAHERTZ.Figure 2-1C.-Interelectrode capacitance in a vacuum tube. INTERELECTRODE CAPACITANCE IN ATUNED-PLATE TUNED-GRID OSCILLATOR.A good point to remember is that the higher the frequency, or the larger the interelectrodecapacitance, the higher will be the current through this capacitance. The circuit in figure 2-1C, shows theinterelectrode capacitance between the grid and the cathode (Cgk) in parallel with the signal source. Asthe frequency of the input signal increases, the effective grid-to-cathode impedance of the tube decreasesbecause of a decrease in the reactance of the interelectrode capacitance. If the signal frequency is 100megahertz or greater, the reactance of the grid-to-cathode capacitance is so small that much of the signalis short-circuited within the tube. Since the interelectrode capacitances are effectively in parallel with thetuned circuits, as shown in figures 2-1A, B, and C, they will also affect the frequency at which the tunedcircuits resonate.Another frequency-limiting factor is the LEAD INDUCTANCE of the tube elements. Since the leadinductances within a tube are effectively in parallel with the interelectrode capacitance, the net effect is toraise the frequency limit. However, the inductance of the cathode lead is common to both the grid andplate circuits. This provides a path for degenerative feedback which reduces overall circuit efficiency.
What is stray capacitance and how is different from ordinary capacitor?
Any two adjacent conductors can be considered a capacitor, although the capacitance will be small unless the conductors are close together for long. This (often unwanted) effect is termed "stray capacitance". Stray capacitance can allow signals to leak between otherwise isolated circuits (an effect called crosstalk), and it can be a limiting factor for proper functioning of circuits at high frequency. Stray capacitance is often encountered in amplifier circuits in the form of "feedthrough" capacitance that interconnects the input and output nodes (both defined relative to a common ground). It is often convenient for analytical purposes to replace this capacitance with a combination of one input-to-ground capacitance and one output-to-ground capacitance. (The original configuration - including the input-to-output capacitance - is often referred to as a pi-configuration.) Miller's theorem can be used to effect this replacement. Miller's theorem states that, if the gain ratio of two nodes is 1/K, then an impedance of Z connecting the two nodes can be replaced with a Z/(1-k) impedance between the first node and ground and a KZ/(K-1) impedance between the second node and ground. (Since impedance varies inversely with capacitance, the internode capacitance, C, will be seen to have been replaced by a capacitance of KC from input to ground and a capacitance of (K-1)C/K from output to ground.) When the input-to-output gain is very large, the equivalent input-to-ground impedance is very small while the output-to-ground impedance is essentially equal to the original (input-to-output) impedance.
What is the effect of stray capacitance in a circuit?
stray capacitance(one that develops between wires ,conductors within the circuit) is obviously not useful as it alters the effective values of circuit components when developed in the oscillators and hence it destabilize the frequency of oscillations Engr.syed mudassir hussain
How does capacitance cause signal degradation?
A capacitor is composed of two conductors that are separated by an insulator. This is a simple definition, but it says a lot about capacitance, and it says it very well. By this definition, there could be capacitance just about anywhere in a power system or circuit. Yes! There could! And there is! Capacitance offers "resistance" to alternating current (AC) signals called reactance. The higher the frequency, the less reactance there is and the better the signal will be able to pass through the capacitor. In modern electronic equipment, there are lots of circuit pathways and lots of components in the circuits. This leads to a lot of distributed capacitance in the circuit. This distributed capacitance represents a lot of little pathways for signals to "jump gaps" in the circuit. Signals will avoid going through the components and devices and also avoid following all the pathways it is supposed to follow. The signals will be "shorted around" components or "shorted to ground" in other pathways. This combines to effect signal loss or degradation. The higher the frequency of the signal put through a circuit, the more loss there will be to the signal due to distributed capacitance.
How does one reduce stray capacitance?
You can reduce stray capacitance by avoiding having long wires running parallel in circuits. Keep wires as short as possible. Long wires running along each other can exhibit stray capacitance effects. Another way is to cut long leads of components such as capacitors and inductors to make them as short as possible. If best, use SM components, as they have no leads which can cause this stray capacitance effect.
What is the type of capacitance effect exhibited in P-N junction when it is reverse biased?
1. Transition capacitance 2. Diffusion capacitance 3. Space charge capacitance 4. Drift capacitance
What is the difference between capacitance and stray capacitance?
Capacitance is an ability to store an electric charge. "If we consider two same conductors as capacitor,the capacitance will be small even the conductors are close together for long time." this effect is called Stray Capacitance.
