555 at higher frequencies

[soundman]

Hello guys,

I want to use a 555 chip at say 8.5MHz, I have choose to use a 1pF cap for the pin 2 to ground of the chip, a 82k for 2 to 7 pin and a 6.8k resistor for the 7 to 8 pin, the output waveforms is not critical, Can you guys tell me if 555 is able to handle that freq?
I know that this chip works just at 500MHz max,but what if I use it at 8.5MHz?

Thanks

 

[JimB]

Hello guys,

I want to use a 555 chip at say 8.5MHz, I have choose to use a 1pF cap for the pin 2 to ground of the chip, a 82k for 2 to 7 pin and a 6.8k resistor for the 7 to 8 pin, the output waveforms is not critical, Can you guys tell me if 555 is able to handle that freq?
I know that this chip works just at 500MHz max,but what if I use it at 8.5MHz?

Thanks

500Mhz !!! In your dreams! Not at 8.5Mhz either.
Maybe in a stupid simulation program, in the real world no way Jose.

JimB
Rolling on the floor having an hysterical fit!

 

[soundman]

sorry it was a typo, I meant 500kHz,

 

[Sceadwian]

What is this for? If it's for RF give the idea up immediately, it will be completely unstable. You obviously have a 555 in mind from the start, but if you tell us what you want to actually DO we might be able to offer better suggestions or chips, you're not giving us much to work with.

 

[Hero999]

An oscillator can be built using CMOS gates which work up to a much higher frequency than a 555.

It's possible to use two gates, but at high frequencies it's not stable or a single Schmitt trigger but it's not very accurate.
**broken link removed**

In this case I think it's better to use three gates because it's stable it high frequencies and more accurate than a Schmitt trigger.


Here's a link to a paper on the subject:
https://www.electro-tech-online.com/custompdfs/2010/05/AN-118.pdf

I'd recommend the 74HC04 or 74HC00
https://www.electro-tech-online.com/custompdfs/2010/05/74HC_HCT04.pdf
https://www.electro-tech-online.com/custompdfs/2010/05/74HC_HCT00.pdf

 

[Mikebits]

Hello guys,

I want to use a 555 chip at say 8.5MHz, I have choose to use a 1pF cap for the pin 2 to ground of the chip, a 82k for 2 to 7 pin and a 6.8k resistor for the 7 to 8 pin, the output waveforms is not critical, Can you guys tell me if 555 is able to handle that freq?
I know that this chip works just at 500MHz max,but what if I use it at 8.5MHz?

Thanks

What is it for?