| 摘要 |
An automatic gain control circuit (10) suitable for use in a modem receiver for receiving a modulated carrier representing data, includes a variable gain amplifier (14) adapted to receive an input signal and coupled to an output amplifier (20) providing the gain controlled output (AGCO) and also coupled to a level detector (30) which provides a high level output signal whenever the input thereto exceeds a reference level, such output signal causing an attack operation wherein a control current generator (48) provides an exponentially decreasing control current (Ic) for an operational transconductance amplifier (50) included in the variable gain amplifier (14). When the level detector output is high for more than a predetermined time a noise hit protection circuit (44) is effective to inhibit the attack operation for a further predetermined period of time, thereby alleviating the adverse effect of a noise pulse. |
