a unique frequency doubler circuit is utilized which requires only a handful of standard components such as operational amplifier , logic gates , resistors , capacitors and switches . in contrast to certain prior art frequency doublers , frequency doublers constructed in accordance with the teachings of this invention do not require the use of a phase lock loop , thereby resulting in a substantial simplification of circuit construction . furthermore , frequency doublers constructed in accordance with this invention utilize a feedback technique which assures that the duty cycle of the output signal will be 50 %, or any other predefined value .