Abstract: An improved frequency synthesizer utilizes a first order loop and sample-and-hold phase detector with optimized gain to obtain very fast frequency locking characteristics. In addition, synchronization of the programming of the loop divider and of the range shifting the voltage controlled oscillator is also utilized. An adaptive loop filter is provided to allow a first order loop to be used for lock acquisition and still maintain excellent noise performance after lock has been obtained.

Abstract: An active power supply ripple filter with low noise and low power dissipation characteristics, which tracks the voltage of the power source with low voltage drop and high current capability. The circuit consists of a control transistor connected between one terminal of a power source and one terminal of a load, a reference circuit which tracks the supply voltage, a low pass filter which filters the reference voltage and an amplifier for driving the control transistor in response to the filtered reference voltage and a feedback voltage from the load. The circuit minimizes the voltage drop across the control transistor as well as minimizing the capacitance values required for the filter capacitors.