Patent ID: 6418303
Filing Date: 2002-07-09
Classification: H03G

Abstract:
A fast attack Automatic Gain Control (AGC) loop having a forward transmission path with an amplifier stage responsive to receipt of a control signal that alters a gain of the amplifier stage and a low pass filter that receives an input and provides a filtered output, the AGC loop further comprising:an off-channel feedback loop, that receives the input of the low pass filter and produces an output fed back to the amplifier stage, having an off-channel detector function and having a one or more off-channel decaying current sources that are capable of being selectably shaped during a decay mode of the AGC loop; an on-channel feedback loop, that receives the filtered output of the low pass filter and applies the control signal to the amplifier stage, having an on-channel detector function and having one or more on-channel decaying current sources that are capable of being selectably shaped during the decay mode; and means within the AGC loop for sequentially and selectively switching out weighted transistors of a plurality of weighted current mirrors at predetermined intervals in order to selectably shape the one or more off-channel decaying current sources and the one or more on-channel decaying current sources during the decay mode.