dB (Decibel)

20 times the log to the base 10 of the ratio of two voltages. Every 20 dBs correspond to a voltage ratio of 10, every 10 dBs to a voltage ratio of 3.162. For instance, a CMR of 120 dB provides voltage noise rejection of 1,000,000/1. An NMR of 70 dB provides voltage noise rejection of 3,162/1.

The standard unit used to express gain or loss of power along a signal path. It indicates the logarithmic ratio of output power divided by input power. A power loss of 3 dB is an attenuation of the incoming signal by half of its original value. A 3 dB power loss is equal to a 6 dB voltage loss. [dB = 10 log P1/P2, P = V¨/R, If R is a fixed value, then: dB = 10 log (V1/V2)¨ or dB = 20 log V1/V2. ] This method of scaling levels becomes important because human sensitivity to sight and sound are logarithmic, which accounts for our large dynamic range capability.

A measure of voltage, current, or power gain equal to 1/10 of a bel. Given by the equations 20 log Vout/Vin, 20 log Iout/Iin, or 10 log Pout/Pin.
See also: Bel.

The standard unit used to express gain or loss of power along a signal path. It indicates the logarithmic ratio of output power divided by input power. A power loss of 3 dB is an attenuation of the incoming signal by half of its original value. A 3 dB power loss is equal to a 6 dB voltage loss. [dB = 10 log P1/P2, P = V¨/R, If R is a fixed value, then: dB = 10 log (V1/V2)¨ or dB = 20 log V1/V2. ] This method of scaling levels becomes important because human sensitivity to sight and sound are logarithmic, which accounts for our large dynamic range capability.