LNA (Low-noise amplifier)LNA is small antenna signal amplifier inside DVB device. Usually it is external component located between antenna connector and RF-tuner. There is usually amplifiers between whole signal path but LNAs and those which are inside of device. Normal LNA we have in digital television device is simple on/off. When it is off it bypass signal, causing still some loss, and when it is on it amplifies signal using some static factor. That factor is called gain and unit used usually is Decibel (dB).
There is also LNAs offering more than one gain level. For example external DVB-T/C LNA NXP BGU7033. It does have 3 modes, 10 dB, 5 dB and bypass -2 dB.
LNAs having even more adjustable gain levels are called variable gain amplifier (VGA). Also there is LNAs/VGAs integrated to the RF-tuner... But I am not going to go deeper these two cases as main need for that LNA API addition is simple external LNAs between RF-tuner and antenna connector.
comments for DVB LNA API
[PATCH RFC] add LNA support for DVB API