Hello sir
After reffering to many areas i got a circuit for 555 as astable with this diagram below
here with R1=1.2k , R2=1k , C= .01 mf , im getting results with online calculator as 45 Khz
but the duty cycle is 68.75 % as it is showing here
So if i want to get 50 % with same frequency out , what measures i ve to take please responce
i completed to many practicals but still having problem in that
thanks
The circuit in post #1 can't achieve 50% duty cycle by nature. There's apparently a problem with the said online calculator or a misunderstanding. A 50% duty cycle circuit is shown in the 555 datasheet. Another popular circuit uses a single resistor between output and capacitor.
Use a D type flip-flop such as a CD4013. Connect the /Q (Q not) output to the D input of one of the flip-flops. Connect the 555 output to the FF clock input. The Q output will be 1/2 the 555 frequency with exactly 50% duty-cycle.
You can also use a JK FF such as the CD4027. Just tie the J and K inputs to the V+ voltage and the 555 to the clock input. Again, the output will be 1/2 the 555 frequency.
Note: Make sure you tie all unused inputs of both FFs to ground.
hmm okk i got it but sir tell me please about the frequency responcing limits for this 4027 etc
cause i hv listened about 555 that it has good responce upto 100 KHgz
so if i need a 50 Khz 50% duty cycle out using filp flops then i ll have to make 100 Khz on 555 timer
& too a problem is here that if i ve to make final output of flip flop to 100 Khz then i hv to make frequency of 200Khz on 555 timer which is practically i guess not possible
hmm okk i got it but sir tell me please about the frequency responcing limits for this 4027 etc
cause i hv listened about 555 that it has good responce upto 100 KHgz
so if i need a 50 Khz 50% duty cycle out using filp flops then i ll have to make 100 Khz on 555 timer
& too a problem is here that if i ve to make final output of flip flop to 100 Khz then i hv to make frequency of 200Khz on 555 timer which is practically i guess not possible
I don't understand your question. Are you asking about where and how to order a 555? Since I don't know where on "earth" you live, I can't really help you there. (Now if you were on Mars, I may know a place. :wink
hahaha no no actually i am asking the proper number or say a code including the 555 labelled on tha i.c. . . Are all 555 i.c.s available in market relating CMOS family ?