I have been working on a concept circuit using a 555 timer that is based on the old trusty 555 Hysteretic Oscillator. It would look some thing like this.
The result would be both a square wave and triangle wave in the same circuit. Hey, I like technical challenges. The problem is the requirement for a really low current self contained Constant Current (CC) regulator. Higher Currents are easy. The LM317 will handle 10ma to 1A very well.
So now I need to create a CC regulator that can go down to 100 µa . My first experiment was this:
I realized the base current was way too large and I needed to reduce the base interaction to at least 10% of the target current. So this was my next brain fart:
This didn't work either due to the current being so low it was on the knee of both diodes forward conduction area.
Other design criteria revolves around the 555 circuit, if it is powered by +12V then the minimum voltage for the current regulator is 1/3 Vcc (4V), and the max voltage is 2/3 Vcc (8V). The only other design I know of that might work one I have never used based on a JFET. Before I run out and buy a couple to play with I thought I would open up a discussion on the forum. Any thing besides 2 wire CC regulator is off topic. I am not asking for a triangle wave generator circuit.
The result would be both a square wave and triangle wave in the same circuit. Hey, I like technical challenges. The problem is the requirement for a really low current self contained Constant Current (CC) regulator. Higher Currents are easy. The LM317 will handle 10ma to 1A very well.
So now I need to create a CC regulator that can go down to 100 µa . My first experiment was this:
I realized the base current was way too large and I needed to reduce the base interaction to at least 10% of the target current. So this was my next brain fart:
This didn't work either due to the current being so low it was on the knee of both diodes forward conduction area.
Other design criteria revolves around the 555 circuit, if it is powered by +12V then the minimum voltage for the current regulator is 1/3 Vcc (4V), and the max voltage is 2/3 Vcc (8V). The only other design I know of that might work one I have never used based on a JFET. Before I run out and buy a couple to play with I thought I would open up a discussion on the forum. Any thing besides 2 wire CC regulator is off topic. I am not asking for a triangle wave generator circuit.