AGC Fundamentals

  • Juan Pablo Alegre Pérez
  • Santiago Celma Pueyo
  • Belén Calvo López
Part of the Analog Circuits and Signal Processing book series (ACSP)


From a practical point of view, the most general description of an AGC system is presented in Fig. 2.1. The input signal V IN is amplified by a variable gain amplifier (VGA), whose gain is controlled by a signal V C . In order to adjust the gain of the VGA to its optimal output level V OUT , the AGC generally, first detects the strength level of the signal using the peak detector; it then compares this level with a reference voltage V REF and finally, it filters and generates the required control voltage. This function can be performed by detecting the signal at the output of the VGA, so the architecture is called “feedback” AGC(Fig. 2.1a), or at the input, in which case it is identified as “feedforward” AGC (Fig. 2.1b) [1].


Control Voltage Peak Detector Loop Filter Feedforward Loop Variable Gain Amplifier 
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Copyright information

© Springer Science+Business Media, LLC 2011

Authors and Affiliations

  • Juan Pablo Alegre Pérez
    • 1
  • Santiago Celma Pueyo
    • 2
  • Belén Calvo López
    • 2
  1. 1.LSI CorporationMadridSpain
  2. 2.University of ZaragozaZaragozaSpain

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