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 A Level     Signal     ADC Flash     ADC Ramp     DAC Summing     Distortion     Problems     Regenerator     Sample and Hold     Sampling     Serial and Parallel     >signal to noise ratio<

# Signal signal to noise ratio

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## The Decibel Scale

The decibel (dB)  scale is logarithmic. Log scales have the advantage of representing a huge range of values with quite a small range of numbers.

## Power Gain

The gain could be a loss called attenuation.

Gdb = 10 log10 ( POUT / PIN )

## Combined Gain of Several Stages

• Voltage, current or power gains expressed as ratios multiply.
• Gains expressed in dB add up.

## Signal to Noise Ratio

The signal is wanted. The unwanted electrical noise comes from external sources like lightning strikes, industrial machinery power switching, or warm components in sensitive electronics.

For Power        SNRdb = 10 log10 ( PS / PN )

For Voltage      SNRdb = 20 log10 ( VS / VN )

## Conversions between Power Gain and dB

Ratio dB
POUT/PIN     10 log10(POUT/PIN)
10 000 000 000  100
1 000 000 000  90
100 000 000  80
10 000 000  70
1 000 000  60
100 000  50
10 000  40
1 000  30
100  20
10  10
0.5  −3
0.25  −6
0.1  −10
0.01  −20
0.001  −30
0.0001  −40
0.00001  −50
0.000001  −60
0.0000001  −70
0.00000001  −80
0.000000001  −90
0.0000000001  −100

## Conversions between Voltage or Current Gain and dB

Ratio dB
Vout / Vin
Iout / Iin
20 log10 ( Vout / Vin )
20 log10 ( Iout / Iin )
100 000  100
10 000  80
1 000  60
100  40
10  20
1.414
0.707  −3
0.5  −6
0.1  −20
0.01  −40
0.001  −60
0.0001  −80
0.00001  −100

## The Universe with a Log Scale

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 CloseEscapeX Q: qNum of last_q     Q ID: Question ID         Score: num correct/num attempts         Date Done

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