What's the difference between AGC and ALC?

[htforever]

alc agc

Of course, AGC means Auto Gain Control,
AGL means Auto Level Control,
But can anyone explain it in detail for me? Or introduce some classic books about them?
Thanks very much!

 

[jon2000]

agc vs alc

My understanding is that AGC refers to receiver and ALC refers to transmitter.

An AGC amplifier (usually in IF stage) maintains a constant output level while the input receiving signal varies across a very wide dynamic range.

An ALC normally has a known input signal level and it is used to adjust the output level (such as audio volume, RF power, etc.).

 

[flatulent]

agc alc

There is also AVC which stands for automatic volume control. These terms all mean about the same thing, but custom has assigned different terms to different equipment classes. They all mean varying the transfer function so that the output is a constant value with changing input.

 

[colombo2]

agc & alc

AGC typically applies to receivers. In any band of frequencies, there exists the channel you want to receive plus interferers. To guarantee certain SNDR at the ADC output, you need to have a particular input signal amplitude to the ADC. If your channel is weaker that that level, you need to re-adject the gains in the receiver chain to get your channel level right and vice versa.

ALC refers to level adjustment loops. This can be applied to any circuit not an entire system or sub-system. A prime example is ALC loops used to regulate oscillator's amplitude to suppress amplitude noise or reduce current 0ver-design factors.

Colombo2

 

[lcg22]

alc vs agc

Anther question, how to measure(not the definition) the SNDR? Thanks.

 

[htforever]

alc versus agc

I searched google and found: In TV amplifier, ALC means AGC+ASC(Automatic Slope Control).
AGC: Use power level at one frequency point as a reference to control the gain of amplifier;
ASC: Need to detect power level information at two different frequency points to adjust the slope of gain to frequency. So In this situation, ALC is much more complex than AGC.