Good morning everyone,
I'm designing a 555 astable oscillator.
The characteristics are:

T(s)=33,33uS
F(Hz)= 30Khz
Duty(%)=60%
Th=20uS
Tl=13,33uS

Using a software I got the values for the resistors and for the capacitor

R1=9,62K = 10K
R2=19,24K= 20K
C=1nF

My question is: where do I find the 1nF capacitor? Does it exist? What can I do?

Thanks for your help

Albertino

 

1nf = 0.001µF

Common as dirt, any electronics store.

http://www.radioshack.com/product/index.jsp?productId=2062362

 

Hi All,
You have to be a bit careful about the type of cap you install for the timing cap (1 nF). It will largely depend on the accuracy & stability that you need. Since I don't know what you are using it for, I cannot help you here unless you reply with more detailed specs for your astable. But, generally, an NPO dielectric is the most stable and one of the most expensive. IT is great for both innitial accuracy and stability over a wide temperature range and over time. If you only need +/-10% or +/-20% accuracy and stability, then go ahead and use a standard monolithic ceramic or even a cheap ceramic disk cap. The timing is largely independent of the power supply voltage since it works on the ratio of the supply voltage (about 1/3rd for low threahold and 2/3rds for the hi threshold if my memory is correct). There are two basic versions of the 555. The bipolar and the CMOS. I amost always prefer the CMOS as it uses far less bias current, can operate at higher frequencies, can operate over a wide range of power supply voltages, and a few other things I can't remember off the top of my head at present. Although the bipolar is a good unit too, it's just that it has more limitations. Please feel free to contact me or reply with more questions.

 

I use 1nF 5% metalized film capacitors that have good temperature stability.