Harmonic Content? 555 vs CD4069 oscillator ??

[royalmp2001]

Can anyone tell me how the harmonic content of a CMOS 555 squarewave
oscillator may compare to a 2 hex invertor oscillator from a CD4069.

I think I heard that the 7555 can produce richer harmonics... but can
anyone explain if this is true and why?

 

[Andrew Holme]

royalmp2001 wrote:

Can anyone tell me how the harmonic content of a CMOS 555 squarewave
oscillator may compare to a 2 hex invertor oscillator from a CD4069.

I think I heard that the 7555 can produce richer harmonics... but can
anyone explain if this is true and why?

It depends on the steepness of the edges. If you look at the datasheets,
and compare their rise and fall times, the device with the faster edges has
more power in the higher harmonics.

 

[Bob Masta]

On 18 Aug 2005 07:53:51 -0700, "royalmp2001" <royalmp2001@hotpop.com>
wrote:

Can anyone tell me how the harmonic content of a CMOS 555 squarewave
oscillator may compare to a 2 hex invertor oscillator from a CD4069.

I think I heard that the 7555 can produce richer harmonics... but can
anyone explain if this is true and why?

Not sure exactly what you mean by "richer" harmonics. A perfect
square wave has only odd harmonics. If you change the duty
cycle from 50-50, you add even harmonics as well. You might
want to try a really narrow pulse train.


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator

 

[Ralph Mowery]

"Bob Masta" <NoSpam@daqarta.com> wrote in message
news:4305cacd.1326293@news.itd.umich.edu...

On 18 Aug 2005 07:53:51 -0700, "royalmp2001" <royalmp2001@hotpop.com
wrote:

Can anyone tell me how the harmonic content of a CMOS 555 squarewave
oscillator may compare to a 2 hex invertor oscillator from a CD4069.

I think I heard that the 7555 can produce richer harmonics... but can
anyone explain if this is true and why?


Not sure exactly what you mean by "richer" harmonics. A perfect
square wave has only odd harmonics. If you change the duty
cycle from 50-50, you add even harmonics as well. You might
want to try a really narrow pulse train.

That is the problem. There is no perfect square wave. To do this the
harmonics would have to extend to infinity. The voltage ouput would have to
go from maximum to zero in zero ammount of time. Still not possiable in
real life. Some devices will turn off and on faster than others . This
makes them "richer" in harmonics than slower devices. The 555 takes longer
to switch than the 4069.