Nicholas Gray (cncgsc@tevm2.nsc.com) wrote: : John Albert wrote: : > : > Does anybody have any ideas on how to build a : > frequency doubler. I would like to take a square : > wave signal (0 to +5v) and double the input : > frequency. The input frequency can vary between : > 1Khz and 500khz giving 2Khz to 1Mhz output. : The most simple way to do this is to use an exclucive-or (XOR) gate and : an inverter or two: : _____ : INPUT -------------| | : | | | : | |\ | XOR |----- OUTPUT : --| >O-----| | : |/ |_____| : This circuit produces rather narrow output pulses. You can make these : pulses wider by using two inverters in series where I show one inverter. This approach will not be practical for the huge frequency range he wants. Even a relatively narrow glitch at 2KHz will be longer than the entire period at 1MHz. The only sensible alternative is to use a simple PLL (like the 74HC4046) and a divide by 2 flip flop in the feedback loop. All you need is the 74HC4046, a 74HC74, 2 resistors and a cap. The output is a 5% duty cycle at all frequencies. Beats the heck out of a glitch pulse output. Bob.
Date: 11 Jul 1996 22:07:52 GMT
Original Subject: Re: Frequency Doubler