Diode Voltage Drop Solutions: Low-Drop, One-Way Conductivity & Adjustable Zener Diodes

I'm not sure this is a good forum for such questions, but I haven't found a better one :)

Well, the following problem bothers me:
The voltage drop on an ordinary silicon diode during conduction is about 0.6V. On the light emitting diode - about 2V, depends on the color of the light.

And now the questions:

Are there diodes where the voltage drop would be smaller, e.g. 0.3V?
Is there any "one way conductive" component that would not have a voltage drop?
Is there a regulated zener diode where the voltage drop could be adjusted from 0 to 1V?

thank you in advance for your help.

ad. 1.yes, they are Shotky diodes,
ad. 2.No such elements (depending on the application, you can use a linear rectifier, i.e. a rectifier built on the basis of an operational amplifier and a diode)
ad. 3. any zener diode and appropriate selection of a resistor divider + potentiometer.

You will get 0.3V on each germanium diode.

Tdv wrote:

ad. 3. any zener diode and appropriate selection of a resistor divider + potentiometer.

And such a schematic would be able to include?

ad 1 if you take, for example, a 100 amp flash diode and if you pass only 0.1 A through it, you will have a drop even below 0.1V
ad 3 - tl431 such a cheated zener diode

Re, john_doe, take it easy. Fatal examples.
Greetings

bobo

http://elenota.iele.polsl.gliwice.pl/download.php?id=44009

pdf for tl 431 - regulated zener diode in practice ...

Re, john_doe, read the notes (TL431) carefully
1. is a programmable zener diode - not deceived and adjustable
2. a precise voltage reference source
3. operational amplification
Greetings

tricked - because it's regulated
and they are programmed with galas and microcontrollers :P

low-voltage adjustable precision shunt regulators

mojomax wrote:

1. Are there diodes where the voltage drop would be smaller, e.g. 0.3V?
1. Is there any "one way conductive" element that would not have a voltage drop?
3. Is there a regulated zener diode where the voltage drop could be adjusted from 0 to 1V?

1. I think enough has been answered already; one could still consider LEDs
from other materials - except that the lower the voltage drop across the diode, the greater
reverse current - e.g. a diode that conducts 1A at 0.2V must have a reverse current
at least 1mA - this is due to thermodynamics; I guess the diodes are reversed
and tunnel diodes are not subject to this limitation - inverted diodes (so called because
that they let the current pass in the reverse direction and they retain it in the forward direction
like any normal diode - they conduct at about 0.6V), they are very sharp
transition between breakdown (reverse current) and no current at
low voltage in the forward direction; tunnel diodes have this breakdown to
a certain small voltage in the forward direction and when increasing the voltage
you reach an area where they are not yet very conductive, and breakthroughs are already
there is none, so the forward current decreases with increasing voltage - incl
in the range it is impossible to measure their characteristics - and still they conduct normally;

2.How to be zero voltage drop, reverse current is like conduction;

3. there are ICs that are voltage standards, and you can use them instead of diodes
Zener (they are much more accurate than them, have lower impedance, and above all
all by adding two resistors we set their "zener voltage") - but
their minimum operating voltage is 1.225V; maybe if such a system was made of another
material, e.g. germanium, it would be slightly smaller - around 0.8V, but it is not
it's easy, germanium gives too much reverse current; with lower tensions worse;
well, unless we lower the temperature, at the temperature of liquid nitrogen one could ...

Oh, and a curiosity - there is such a thing as a Josephson junction (at a temperature of
liquid helium - I do not know if it is possible in higher): at _zero_ voltage it lets go
current, but not at non-zero - starts to behave like an insulator; and more specifically,
it runs a current with a frequency proportional to the voltage, and these are quite large
frequency, so it is difficult to notice this current ...

Ad 2 one-way conductive element ... sees zero (short-circuit of the relay) without the possibility of sensing the polarity ... but if you can tweak it with a comparator ... as you can see, even if you pull the results, at most a voltage drop would be a drop on the wires, contacts, relay plate ...

and there are many disadvantages to such a mechanical field ..

In the past, selenium rectifiers were used, and copper ones, I do not remember the characteristics of copper junctions, but if I remember correctly, they were not satisfactory.

Rectifiers are made without voltage drop. It is a split transformer, where mosfets are turned on instead of 2 diodes. These mosfets are controlled by comparators powered by another traditional power supply. You can meet such miracles in very expensive power amplifiers.

I had a camera smd diode with a drop of 0.02V in my hand. It was the peak of this measure, so I will not give the exact value. Most of the LEDs have as much after burning (both sides), but this one was 100% functional.

It is true with MOSFETs (approximately - the best ones have a resistance of about 3 milliohms),
only it's not a diode anymore, and requires a few volts to be driven at the gate.

And a diode with a forward voltage of 0.02V - if it is a regular PN junction, not some
a wonder with quantum effects such as a tunnel diode or an inverted diode - it transmits into the other
the side of the current is comparable to the conduction current (unfortunately this is due to thermodynamics,
as long as the current carriers move independently, without creating any Cooper pairs).

The diode current is described (without taking into account the voltage drops on the contacts,
and on semiconductor resistance, surface currents, and breakdown) by the formula

Quote:

I = I0 * exp (U * e / (k * T))

where e = carrier charge, k = Boltzmann constant, T = absolute temperature,
U = voltage at the junction, I0 is temperature dependent (it should be proportional
do exp (-deltaE / (k * T)), where deltaE = width of the energy gap of the material;
for silicon deltaE = around 1.225eV - therefore for precise voltage patterns it does
to such a voltage, just the reference voltage is the gap width - this
is not exact, the width of the energy gap is temperature dependent, it is
a little lower, but when you put in this voltage, the relationship is good).
At room temperature, k * T / e is about 27mV if e is an electron charge.

If the diode is to give a "sharper" voltage-current dependence, it has to be lowered
temperature, or try to get through the junction instead of individual media
their groups have gone through - e.g. Cooper vapors, or even better, condensate
Bose-Einstein from such pairs - then even a picovolt can strongly change the current ...

I see that _jta_ has knowledge of solid state physics like my teacher from an electronic high school. Did you study any such field? Because when I read your post, it was as if I was at a lesson in electronics, my grandmother was extremely familiar with semiconductor theory and more, I couldn't come out in awe.

As I will remember, I will throw here a schematic of such a "diode" on the MOSFET from the Elector. Maybe that will clear things up a little.
Regards.

ad 2 acc. This tdv gave me the best solution - for low power and medium frequencies, the active rectifier is probably the best / simplest solution ... it is cheap to implement and there is a resistance of solutions (from the simplest to the more complicated) available in practically every book with the inscription analog electronics. .
as for high power, I do not see a problem in the use of ordinary rectifier diodes because there are quite a lot of voltage, and in the high power technology it is already a problem ...

Pi-Vo wrote:

Have you studied any such field?

I studied physics at the University of Warsaw. Besides, I was a bit interested in these things.
The description of the tunnel diode and the inverted diode can be found in the three-volume "Encyclopedia of Physics".
The formula for the characteristics of an ordinary diode also.

And here is this MOSFET control chip, which imitates a diode with a low voltage drop.
Regards.