Hey guys, I am building a clock using ATTINY13A. This micro doesn't have a crystal input, only a clock input, it can't use a resonator. Other than this issue, it is just what I need and it's super cheap, which is also really awesome, since I actually am considering making the thing into a soldering kit once it's all done... It also has extremely low power consumption (below 1uA@32khz).
Any other micros in this price range (~50c) don't operate at voltages this low and their power consumption is orders of magnitude higher. They usually also feature additional pins or functionality I won't be using. They are sometimes also bigger, which increases the PCB size and further increases the price!
So I was thinking about building an oscillator. I found this circuit:
I built it on breadboard. (well, not really, I changed some values, but it didn't really seem to change much).
The thing is, it's allegedly 1vpp with 1v offset @3V. I couldn't really confirm that, since the output impedance is so large my scope significantly affects it. In fact, it affects it in such a way, that it doesn't really even start without the scope there though, it seems... I tried to measure it with a multimeter, and it didn't really measure anything, so I suppose it needs some sort of larger load to start.
My question is:
Can I hope to be able to make some changes, which will make this (or similar) circuit a reliable clock source for tiny13a? The datasheet says it should have 50% duty cycle. I am not sure how to amplify this signal. Maybe I could high-pass it and then feed it into a mosfet. But I didn't find a cheap mosfet with less than 2V guaranteed gate threshold, and the batteries will go down to 1.8V... .-. Hoofsorting mosfets to see which one is okay is kind of time consuming. Plus I am not sure if a mosfet (rumor has it those are electrostatic sensitive) would make a good part of a soldering kit. And I can't really hope to use a bipolar transistor, I suppose, right?
I was considering using a dual opamp, but I can't find any with idle power (current) consumption around 1uA in my price range.
Also, if this circuit can't be used, is there some similar with current consumption around 1-10uA? Couldn't find any... Thanks a lot!