Gain of Gain DB db

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A decibel (decibel) is a unit that measures the number of two units in the same unit, primarily for measuring sound intensity, commonly used in DB .

"Sub" (deci-) refers to One-tenth, the digit is "shellfish" or "Bell" (BEL), but generally only use decibels.

Decibel (db) is one of the most important Bell (b): 1 B = 10dB.

Power Quantity

When considering power or strength (intensity), the ratio can be expressed in decibels, which is calculated based on the 10 logarithm of the ratio of the measured value to the reference value, multiplied by 10.

Therefore, the ratio of power value P1 to another power value of P0 is expressed in decibels as LDB:

The ratio of two power values is based on a logarithm of 10, which is the Bell (BEL) value.

The decibel value of the two power value is 10 times times the value of the bell (or, 1 decibels is one of the bell).

P1 and P0 must measure the same numeric type, with the same units.

If P1 = P0 in the upper formula, then LDB = 0.

If P1 is greater than P0, then LDB is positive;

If P1 is less than P0, then LDB is negative.

The formula for calculating P1 can be obtained by rearranging the upper type, according to P0 and LDB:

Because Bell is 10 times times the decibel, the corresponding formula for using the Bell (LB) is

All examples are dimensionless decibel values, because they are the decibel representation of the ratio of two quantities to the same dimension.

"DBW" indicates that the reference value is 1 watts, and "DBm" indicates that the reference value is 1 MW.

Note that the

Explains that the definition above has the same value--

Whether the power value or the voltage amplitude is calculated, as long as the ratio of power in a particular system is proportional to the square of the amplitude ratio.

There are many advantages to using decibels:

• A decibel is actually a numeric value, so a very large ratio can be expressed in the usual quantities, which can clearly represent a very large number of changes.
• The overall gain of a multi-component system, such as cascaded amplifiers, can be calculated directly by adding the gain decibel of each component.
  You do not need to multiply these gain values (for example, log (AXBXC) = log (A) + log (B) + log (C)).
• A person's perception of strength, such as sound or light, is closer to the logarithm of strength than the strength value itself,
  According to the Weber theorem, the decibel value can be used to describe the perceived level or differential.

In electronics, the ratio (gain) of power or amplitude is usually expressed in decibels, rather than the usual arithmetic ratio or percentage.

One benefit is that the total gain of a system consisting of some column components is the sum of the gain of each component.

A combination of DB and suffix, indicating the reference value when calculating the ratio. For example, dbm indicates the number of decibels with a ratio of 1 mw to the power value.

If the reference value of the decibel is given explicitly and exactly, then the decibel value can be used as the absolute amount,

As measured by the amount of power or the amount of the field. For example, 2 dbm is 10 MW.

Since the decibel is defined by power, it is necessary to convert the voltage ratio to decibels, which must be 20 times times the logarithm.

Before the decibel is deafening, it may be better to gently align the detector with a loud decibel reading.

This may be because the scream only brings the energy in the air, but the air particles directly hit the decibel detector,

Causes additional "0 distance" sound waves to achieve greater positive growth parameter values

Gain

gain in electronics, usually the ratio of the signal output of a system to the signal input.

such as 5 times times the gain, that is, the system makes the voltage or power increase by 5 times times.

The gain is mainly applied to the amplification circuit.

logarithmic units and decibels

In electronics, the gain is often measured in logarithmic units and is used as a unit of the Shell (BEL):

Gain = log10 (P2/P1) Bel

The P1 and P2 respectively are the input and output power.

Since the gain value is usually very large, it is generally used in decibels (db, 10 per 1 of the shell) to indicate:

Gain = 10xlog10 (P2/P1) DB

A similar unit uses the natural logarithm , called Neper.

When the gain is calculated in terms of voltage rather than power, the Joule law (Joule's law,p=v2/r) is used, and the formula is:

• Gain =10xlog10 ((V22/R)/(V12/R)) DB

=10XLOG10 ((V2/V1) 2) DB

=20XLOG10 (V2/V1) DB

This formula is correct only if the load impedance is equal (impedance matched).

In many modern electronic equipment, because of low output impedance and high input impedance, the load can be ignored without significantly affecting the calculation results.

Example

If an amplifier outputs a load of 1 volts to 1 ohms, the output power provided is 1 watts.

If the amplifier is tuned to the output of 10 volts to the same load, it provides an output power of 100 watts (P=V2/R).

Therefore: voltage gain = 100/10 = 10 times times

P = v²/r

Power Gain = (100²/r)/(10²/R) = 100 times Times

By definition, its power gain is 10log100 = db

If the gain is 1 or 0 DB, i.e. the output voltage equals the input voltage, this gain is also known as Unity gain .

Power gain ( English:Power gain) refers to the ratio of the output power to the input power in a circuit.

Unlike other signal gain, such as voltage gain and current gain, power gain is sometimes somewhat confusing because of the relatively vague definition of "input power" and "output power" itself.

Three important power gains include:

• Op Power Gain ( English:operating Power gain),
• Convert power gain (transducer power gain) and
• Effective power gain (available power gain).

It should be noted that the above three gain definitions are based on the average effect of power, not instantaneous power, but the word "average" is often omitted and in some cases causes confusion.

The amplification factor, also called gain, is the extent-which an analog amplifier boosts the strength of a signal.

Amplification factors is usually expressed in terms of power.

The decibel (DB), a logarithmic unit, is the most common-of-the-quantifying the gain of an amplifier.

For power, If the output-to-input signal power ratio are 1:1, then the amplification factor is 0 DB.

A doubling the signal strength (an output-to-input power ratio of 2:1) translates into a gain of 3 dB;

A tenfold increase in power (output-to-input ratio of 10:1) equals a gain of ten DB;

A hundredfold increase in power (output-to-input ratio of 100:1) represents DB gain.

If the output power is less than the input power, the amplification factor in decibels is negative.

Power amplifiers typically has gain figures from a few decibels up to about DB.

sensitive amplifiers used in Wireless communications equipment can show gain of up to approx.

If higher gain is needed, amplifiers can being cascaded, that's, hooked up one after another.

But there was a limit to the amplification so can be attained this.

When amplifiers is cascaded, the later circuits receive noise at their inputs along with the signals.

This noise can cause distortion.

Also, if the amplification factor is too high, the slightest feedback can trigger oscillation,

Rendering an amplifier system inoperative.

Amplifier Gain & Decibelsvoltage Amplification

The Voltage amplification (AV) or Gain of a Voltage amplifier are given by:

With both voltages measured on the same (i.e. both RMS, both peak, or both peak to peak),

Av is a ratio of how much bigger are the output than the input, and so have no units.

It is a basic measure of the Gain or effectiveness of the amplifier.

Because the output of an amplifier varies at different signal frequencies,

Measurements of output power, or often voltage, which is easier to measure than power,

is plotted against frequency on a graph (response curve)

To show comparative output across the working frequency band of the amplifier.

Logarithmic Scales

Response curves normally use a logarithmic scale of frequency, plotted along the horizontal x-axis.

This allows for a wider range of frequency to is accommodated than if a linear scale were used.

The vertical y-axis is marked in linear divisions and using the logarithmic units of decibels

Allowing for a much greater range within the same distance.

The logarithmic unit used is the decibel, which is one tenth of a Bel,

A unit originally designed for measuring losses of telephone cables,

But as the Bel are generally too large for most electronic uses, the decibel (DB) is the unit of choice.

Apart from providing a to convenient scale the decibel have another advantage in displaying audio information,

The human ear also responds to the loudness of sounds on a manner similar to a logarithmic scale,

So using a decibel scale gives a more meaningful representation of audio levels.

Power Gain in DBs

To describe a change in output power over the whole frequency range of the amplifier,

A response curve, plotted in decibels are used to show variations in output.

The powers at various frequencies throughout the range is compared to

A particular reference frequency, (the mid band frequency).

The difference in power on the mid band frequency and the power at any other frequency being measured,

is given as so many decibels greater (+db) or less (-DB) than the mid band frequency,

Which is given a value of 0dB.

Notice that, on the logarithmic frequency scale in Fig 1.3.1 the middle of the 10Hz to 100kHz band is 1kHz

And frequencies around this figure (where the output was usually at its maximum)

is normally chosen as the reference frequency.

Converting a power gain ratio to dBs are calculated by multiplying the logs of the ratio by 10:

Where P1 is the power in mid band and P2 is the power being measured.

Note:when using this formula in a calculator the use of brackets is important,

So then x the log of (P1/P2) is used, rather than x the log of P1, divided by P2.

e.g. if P1 = 6 and P2 =3

Ten x log (6/3) =3db (right answer), but x log 6/3 = 2.6dB (wrong answer).

Voltage Gain in DBs

Although it is common to describe the voltage gain of a amplifier as so many decibels,

This was not a accurate use for the unit really.

It is OK to use decibels to compare the output of a amplifier at different frequencies,

Since all the measurements of output power or voltage is taken across the same impedance (the amplifier load),

But when describing the voltage gain (between input and output) of an amplifier,

The input and output voltages is being developed across quite different impedances.

However it is quite widely accepted to also describe voltage gain in decibels.

When voltage gain (AV) or current gain (Ai) was plotted against frequency the−3db points is where the gain falls to 0.707 of the maximum (mid band) gain.

Notice that converting voltage ratios to DBs uses log (Vout/vin)

Describing the voltage gain of an amplifier that produces an output voltage of 3.5V for a input of 35mV as being 40dB ,

is equivalent to saying that the output voltage is the times greater than the input voltage.

To reverse the process, and convert dBs to a voltage ratios for example, use:

Note that the brackets is important and antilog may is shown on calculator keypads as 10x or 10^

And is also usually Shift +log.

Use the same formula for DBS-to-current gain-ratio, and to-convert dBs to a power ratio, simply replace the form ULA with 10.

An advantage of using DBs to indicate the gain of amplifiers are that in multi stage amplifiers,

The total gain of a series of amplifiers expressed in simple ratios, would is the product of the individual gains:

AV1 x Av2 x Av3 x Av4 ... etc.

This can produce some very large numbers,

But the total of individual gains expressed in dBs would is the sum of the individual gains:

AV1 + Av2 + Av3 + Av4 ... etc.

Likewise losses due to circuits such as filters, attenuators etc. is subtracted to give the total loss.

Commonly encountered DB Values

0dB The reference level to which all +db and−db figures refer.

±1db The least noticeable change in audio levels, also used for the limits of bandwidth on high quality audio amplifiers.

−3db Commonly used for limits of bandwidth in amplifiers, indicating the points where:

A. The output voltage have fallen to 0.707 of the maximum (mid band) output.

B. The output power has fallen to half the maximum or mid band power.

(Half the VOLTAGE amplitude is −6db)

Figures often quoted on attenuators designed to reduce the outputs in signal generators by measured amounts.

−20 DB Signal voltage amplitude divided by 10

−40db Signal voltage amplitude divided by 100

Converting between DBs and Power or Voltage gain

Gain of Gain DB db