Abstract: A voltage-controlled oscillator has a voltage-controlled oscillation circuit that oscillates at a frequency according to a control voltage and a limiter circuit that limits the output of the voltage-controlled oscillator to a predetermined level. This configuration makes it possible to maintain a constant output level irrespective of the oscillation frequency.

Abstract: A conventional up/down Gray code counter has both a logic circuit section for up counting and a logic circuit section for down counting, and thus has a large circuit scale. To overcome this inconvenience, an up/down Gray code counter of the invention has a one-way Gray code counter that can count only in one, up or down, direction and a highest bit selecting circuit that receives the highest bit of the data output from the one-way Gray code counter and that then outputs the bit selectively either intact or after inverting it.

Abstract: A conventional up/down Gray code counter has both a logic circuit section for up counting and a logic circuit section for down counting, and thus has a large circuit scale. To overcome this inconvenience, an up/down Gray code counter of the invention has a one-way Gray code counter that can count only in one, up or down, direction and a highest bit selecting circuit that receives the highest bit of the data output from the one-way Gray code counter and that then outputs the bit selectively either intact or after inverting it.

Abstract: Conventionally, it is difficult to design the logic of a Gray code counter that can be used in interlaced counting. Even though interlaced counting is possible with a Gray code counter, the number of simultaneously changing bits increases greatly depending on the number of counts skipped at a time. To overcome these problems, a Gray code counter according to the present invention has a consecutively counting Gray code counter that counts in increments or decrements of one, and an output value converter circuit that converts the Gray code data output from the consecutively counting Gray code counter into a Gray code corresponding to decimal counts as obtained by counting with (2 raised to a particular power minus 1) counts skipped at a time.