Perfect 50 Percent Duty Cycle 555 Timer

145

01:23:48

This uses two inverters to amplify the signal from the 555 timer output (one to remove the 1.5V voltage drop and the other to provide current) and feed it to the inputs through a resistor and capacitor. Since the capacitor is charged/discharged with the same current it results in a perfect 50% duty cycle.

published 7 years ago

7 years ago

its duty will be effected by the two triodes. so it's better to generate a square wave by 555 first and then to amplify it

jason9

7 years ago

Triodes? You mean the BJTs? Triodes are the vacuum tube (valve) analog to silicon transistors. The transistors quite effectively channel either the full power supply or ground, and since the 555 threshold and trigger are at exactly 1/3 and 2/3 power supply, it should be exactly 50% duty cycle which is theoretically impossible to achieve with the standard astable 555 setup.

7 years ago

You're right. My English is poor. I mean you can genarate a perfect square wave by 555 itself. Pin 3 via a res to pin 2,6. pin 7 is floating.

jason9

7 years ago

That what I have set up here. Just a few extra components to boost the output signal to full 5V since it only goes to 3.5V on it’s own. If it were at 3.5V then it would take much longer to rise.

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