| 摘要 |
An automatic gain control circuit wherein the gain progressively increases in increasingly larger magnitudes. The illustrative embodiment includes an amplifier whose gain is related by a voltage follower to the voltage on a capacitor in a feedback loop. A rectifier develops a signal representing the AGC output level which is compared against a threshold value. A current source, arranged in a further feedback loop with the capacitor and the voltage follower, increases the voltage on the capacitor as a function of that voltage. The second derivative with respect to time of such function is non-negative. To ensure that there exists a voltage on the capacitor upon which the current source can operate, a starting circuit provides a small, non-zero voltage to the capacitor.
|
