trigger pin to vcc optional?

In the astable mode the trigger pin is almost always shown tied to vcc. Is this an option in this mode?
I have seen it left unconnected in a couple of other astable circuits. In the hundreds of kilohertz...would this be a problem?

Posted by John (riveraj@curtisinst.com) on 11/12/2007, at 15:18 GMT

Trigger pin to vcc optional

If you are talking about the 555 timer I would connect this pin to pin 6 for the astable mode. Normally the astable 555 has 2 resistors and a capacitor arranged from +vcc to Gnd as follows: Resistor 1 from vcc to pin 7, resistor 2 to pins 2&6, capacitor between pins 2&6 and Gnd.

Posted by Robert Neill (varient412@yahoo.co.uk) on 24/01/2010, at 17:23 GMT

Trigger pin to +Vcc

In addition to last reply there is a circuit that shows the trigger2 and threshold6 pins tied via a RC network to the output pin3. The trigger pin can be tied to vcc via a resistor usually in ac coupled apps via a capacitor.

Posted by varient412 on 15/02/2010, at 19:10 GMT