I have shown this schematic once before, but it has been almost 10 years ago. This will create a true Rail to rail output for a standard 555, It allowed me to practice my schematic drawing skills, and I was bored.
Why Rail to Rail?
and what is the big deal about it? When driving a MosFet, you really need a rail to rail signal. A CMOS 555 comes with this feature, but a standard 555 has a very soft upper voltage due to the Darlington high side drivers, It might work as is. it is the might part of the previous statement this circuit addresses. a stock 555 will drive up to 200ma. I can foresee circuits where you need more current drive, as in driving a speaker. This circuit, becomes a non inverting buffer, as the transistors both invert the signal. I consider this a negative, but ce'st la vie. If you want even more drive and an inverted signal you can always add another two transistors.
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Why Rail to Rail?
and what is the big deal about it? When driving a MosFet, you really need a rail to rail signal. A CMOS 555 comes with this feature, but a standard 555 has a very soft upper voltage due to the Darlington high side drivers, It might work as is. it is the might part of the previous statement this circuit addresses. a stock 555 will drive up to 200ma. I can foresee circuits where you need more current drive, as in driving a speaker. This circuit, becomes a non inverting buffer, as the transistors both invert the signal. I consider this a negative, but ce'st la vie. If you want even more drive and an inverted signal you can always add another two transistors.
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