| 摘要 |
PURPOSE: To minimize an outside noise by providing a phase detector, variable current source for limiting the gain of the loop amplifier of the phase detector, programmable data register having an output for setting the variable power source, and controller for limiting the output of the data register. CONSTITUTION: A loop amplifier 38 of an extracted and held phase detector 25 is provided with three current sources 34-36 for controlling the gain of the amplifier 38. The detector 25 is provided with its own phase detector 37, loop amplifier 38, and current source 39 having the three ratio and register control current sources 34-36. The high and low states of a 2 bit output by a data register control which of the current sources 34-36 supplies currents. Then, the gain of the loop amplifier 38 related with a pre-set value is decided by inputs at nodes 30 and 31, and successively decided by an outside gain controller. Thus, an outside noise can be minimized. |
