Steve SchneppFirst, I start all my designs in a simulator. I'm using the one from Paul Falstad, as it is dead simple to use, and working well enough for most of my needs.
I'm using a NE555 to generate a dual voltage power source from a single voltage one. The pattern is very common : a simple capacitor charge pump for each voltage.
I don't need to have a very high or low voltage, as I only need to supply a little more that the voltage drops in the opamp IC.
Note, I also leverage the fact that the NE555 has a rather strong output, and it will be able drive both charge pumps directly without needed to use buffers.
The values I'm using are also rather common as it is only power-of-ten. Which are the most easy to source components.
The diodes will be the very common 1N4148, also ubiquitous to find. Using some Schottky ones like the 1N5711 might be more efficient, but they are more difficult to source.
The circuit is available in the Live Simulation.
Discussions
Become a Hackaday.io Member
Create an account to leave a comment. Already have an account? Log In.
Thanks for the insightful remark, as I didn't really think about it.
Yet, I'm really aiming at using the most common NE555.
But, a order of magnitude computation tells that indeed, using a 5V main voltage might be too close. As 5-1.7-0.7 == 2.6 which when doubled is only 5.2 might be too low indeed.
Let's experiment and see if we need to crank up the main voltage so we can avoid those CMOS versions. I'll just add go to 6xAAA instead of 4xAAA ;)
Requiring a CMOS NE555 is not as hard as using a RROI opamp, but still defeats a little the purpose of the project...
Are you sure? yes | no
Unless you must use parts from your stock, the CMOS 555 is widely available, and inexpensive. They have slightly different numbers, e.g. ICM7555. Check the Wiki article.
Are you sure? yes | no
Make sure you use the CMOS 555 rather than the bipolar 555 so that you get pull-up to Vcc rather than Vcc-1.7.
Are you sure? yes | no