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The problem with a diode may be an overvoltage condition with very low load, as well as significantly larger drop (loss of regulation) on maximum load.
The really elegant solution would be to use a low-dropout regulator ("LDO") to reduce the voltage from 5v to 4.2V. However, the "5V" is not...
Usually when having many equal LEDs such as for illumination purposes one connects multiple LEDs in series. That usually simplifies the driving electronics, but requires also a higher feeding voltage, as all LED voltage drops in one string are added up. For instance for a white LED a...
The general rule is that TV may have a dangerous voltage on its chassis. Therefore the isolation transformer is used.
However, another general rule is that the oscilloscope should be safety grounded. And then no isolation transformer is used for it.
That BradtheRad's construction is essentially a home-made current transformer. There is no magic in making them self, indeed. Still the physics apply: Assuming, that the transformer is made "right enough" to have good magnetic coupling, the current is transformed by ratio of the windings. To use...
Hi,
I assume that the AC is mains frequency current? If yes, there are many possibilities. One is a current transformer, which gives total isolation of the measuring circuit from the monitored current. It is easy to implement. I have seen, that there are even cheap small current transformers...
Well, to be honest, I don't know how to start... I guess the fundamentals. A transistor is not quite exactly like a controllable resistor, because it is not linear in the characteristics (voltage/current relationship is not like a resistor's).
To avoid writing a whole book worth text here, I...
In general, regarding bypass capacitors: Whatever values are recommended by the chip manufacturer, it is worth noting, that type and physical size as well as distance between chip and bypass capacitor and grounding are at least equally important.
On circuit board, the placement of capacitors...
I guess you have problems figuring out the relation between antenna size and wavelength: The usual "prototype" antenna is a 1/2 wavelength dipole, which resonates nicely on received frequency. It's most konwn brother is 1/4 wave antenna, where the ground side substitutes the other half of the...
Also, whatever you do, please consider electrical safety.
It is in general easy to find transformers specified to withstand mains voltage safely. With a capacitive connection you have to use capacitors classified as "Y" capacitors, if they are between mains and user accessible circuits. With...
I absolutely agree, that 741 would not work at all with one input to a voltage rail. However, not even an op-amp with rail-to-rail inputs would work in configurations, if the biasing doesn't allow some headroom both at inputs and outputs. Therefore, the bias must be arranged in-between the...
First, the leakages on a circuit (a printed circuit board) are very small. not milliamps, but much smaller. The guarding usually may be required only, when the current levels are below microamps. That is an answer to your last question: When guarding might be necessary: When the input signal...
First of all, what is active is kind of arbitrary decision, as there is no reason to prefer one for another. However, there are practical reasons and just plain old conventions.
One is the practical transistor technology, which is based on physical properties of semiconductors. It just happens...
If we first assume, that the potential leakage is not enormous, but just a significant fraction of the input current level, then it is easier to figure what happens.
Let's say for illustration that for instance our input works around a range of 1 nA. The a leakage impedance would be in this...
The problem is not what the high-impedance input does, but "everything else" nearby - leaking potentially some disturbing signal to the high-impedance (and therefore sensitive) input.
By having a guard "virtually" at the same potential than the sensitive high-impedance input, there will be...
It might work, at least "sort of". However, it is hardly too optimum way of building an amplified crystal receiver.
I say "sort of", because there are some questionable aspects in the circuitry. Without some modifications, not even "sort of"....
Regarding the power supply connections: I am...
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