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Altera_Forum's avatar
Altera_Forum
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15 years ago

Gain control using fpga

Hi, i have four FIR filters and i want to control the gain in the output of each filter and then sum their outputs. The result is sended to an DAC. it is possible to control the gain in fpga...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

+1 dB means (10^(1/20) = 1.220 ratio (not V). -1dB means (10^(-1/20) = 0.8193 ratio. so all you have to do is scale your 14 bit data accordingly.

for +1dB scale your data level up by 1.22.

for -1dB scale your data level by 0.8193

dB is just ratio, it is not absolute value. Confusion is common and is due to this odd case when a ratio seems like having a unit dB while in maths any ratio of same parameters must be unitless.