Recently Someone showed me an alternative to using a diode in this thread . I will test the idea, when I was a new tech over 40 years ago someone suggested this concept:
.......................................................
................................................................Figure 1
It was total bullcorn. I got 0.7V Vf drop when I got around to testing it. It does make a dandy reference for a constant source however where other model of a transistor is used (transistor as a voltage controlled device), it is not the most stable constant current out there, but it works.
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................................................................Figure 2
Here is a design I was presented with:
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...............................................................Figure 3
Looking at it I can see how it works. I will test it and return the results here.
I use diodes as an occasional voltage reference, but since Vf is temperature dependent. I prefer to use the LM317 and its cousins as a voltage regulator/reference. I can see how Figure 3 is supposed to work, but having been fooled by Figure 1, I am looking forward to testing it, possibly to destruction.
It has obvious limitations, it cannot be used in a diode bridge for power supplies, only in areas where there is already a DC power supply in use. It should make a dandy detector for a powered AM crystal radio. The power is again a necessary requirement. But if you have an audio amplifier, then it might be of use. Time will tell.
Other diodes
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Schottky and germanium diodes both drop 0.3V for a Vf. I am told Figure 1 has no voltage drop, I’ll find out. So here is the test setup (Figure 4), to find out what Figure 1 specifications are.
.........................................
...............................................................Figure 4
I am interested if there are any other alternatives out there I may have never heard of.
Discuss.
.......................................................
................................................................Figure 1
It was total bullcorn. I got 0.7V Vf drop when I got around to testing it. It does make a dandy reference for a constant source however where other model of a transistor is used (transistor as a voltage controlled device), it is not the most stable constant current out there, but it works.
.......................................................
................................................................Figure 2
Here is a design I was presented with:
........................................................
...............................................................Figure 3
Looking at it I can see how it works. I will test it and return the results here.
I use diodes as an occasional voltage reference, but since Vf is temperature dependent. I prefer to use the LM317 and its cousins as a voltage regulator/reference. I can see how Figure 3 is supposed to work, but having been fooled by Figure 1, I am looking forward to testing it, possibly to destruction.
It has obvious limitations, it cannot be used in a diode bridge for power supplies, only in areas where there is already a DC power supply in use. It should make a dandy detector for a powered AM crystal radio. The power is again a necessary requirement. But if you have an audio amplifier, then it might be of use. Time will tell.
Other diodes
.............................................................
Schottky and germanium diodes both drop 0.3V for a Vf. I am told Figure 1 has no voltage drop, I’ll find out. So here is the test setup (Figure 4), to find out what Figure 1 specifications are.
.........................................
...............................................................Figure 4
I am interested if there are any other alternatives out there I may have never heard of.
Discuss.
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