Electronic Fundamentals

Two preconditions must be fulfilled for oscillation of an amplifier:

- The phase shift must be 0 Degree or 360 Degree respectively. - The product of amplification and feedback must be k x v = 1 If the phase shift is not 0 or 360 , the positive feedback can turn into a negative feedback. Oscillation is then not possible any more. If k x v > 1, we are dealing with an amplifier overdrive. The amplifier then operates as rectangular wave generator. Is k x v < 1, the amplifier cannot oscillate. The frequency of an oscillator can be determined via an LC combination. In case of OP it can also be determined via RC combinations. Often an amplitude limiter is installed to prevent an overdrive.

Single−ended Amplifier C−Output Stage

A Class C amplifier is identical to class A but the load is a resonance circuit and the transistor is conductive only for a very short time. This type of amplifier is used in HF-amplifiers like transmitter output stages.

Collpitts-Oscillator

A capacitive voltage-divider circuit is used to generate the feedback. Therefore the name „capacitive three point connection".

(clampers) Operating Principle

A clamper can be compared to a rectifier without load, so the peak voltage of an AC is reached. A capacitor is being charged via a diode, charging it to the peak voltage, across the parallel resistor a slow discharge of the capacitor is possible. Fast changes in input voltage will have (virtually) no influence of the capacitor voltage, they can pass the arrangement. Slow changes in input voltage will allow the capacitor to charge to the input voltage level hence this voltage will not be available at the output. This kind of circuitry can be found in CRT TV and monitors for raster synchronization.

Construction of a clamper

A simple clamper consists of a diode, a capacitor and a resistor. Optional a voltage source can be added to achieve any required voltage level.

Construction (Transistors)

A transistor consists of three sequential semiconductor layers. The operating current flows through the N −layers as well as through the P −layers. A transistor has three terminals: - Emitter - Base - Collector

What does a transistor do in a PCB?

A transistor is a miniature semiconductor that regulates or controls current or voltage flow in addition amplifying and generating these electrical signals and acting as a switch/gate for them.

Transistors (General)

A transistor is used as a fast electronic switch or regulator for small and medium DC voltages and currents. There are N − P −N transistors as well as P − N −P transistors.

Voltage of the Base

As long as the voltage of the base in comparison with the voltage of the emitter does not exceed the diffusion voltage for silicon (0.7 volts), the base −emitter diode will be blocked. If the voltage UBE is increased to a point where it reaches the threshold voltage, the base −emitter diode will become conductive and the current flowing between the emitter and the base will inundate the extremely thin base zone. The base zone contains an extremely low amount of dopant material which means that only a very small number of the charge −carriers reach the base connection. The majority (ca. 99%) of the charge −carriers is swept up by the electric field emanating from the collector and is pulled in that direction.

Cascades

Cascades are often used for the creation of high voltage necessary for cathode ray tubes, Geiger-Müller counters, or igniter boxes. Because of the low current consumption of these devices, cascades are more advantageous than high voltage transformers. The lower current carrying capacity is a disadvantage though. Generally one can say: "The higher the increase in voltage, the lower the current carrying capacity." "The basic principle is that of a rectifier circuit."

Diodes in Parallel

Connecting diodes in parallel is possible in general but has several limitations. Such a parallel connection is used when the forward current exceeds the maximum forward current of an individual diode. The total current in forward direction is the sum of the individual currents of the diodes. As the current heats up the diodes their threshold voltage will decrease. As the current distribution across the diodes should be symmetric all the diodes should be from the same production batch and must have the same temperature which could mean they have to be mounted on the same heat sink. If this can not be granted a resistor has to be connected in series with every individual diode. As such a resistor will create losses it should have a very low resistance.

Free-wheeling diode

Diodes can also be used to short-circuit the back-emf that occurs when switching off relays. emf means electromotive force. If the relay is supplied with DC the diode will operate in reverse direction. If the power supply is switched off, the inductivity will generate the back-emf. This voltage will operate the diode in forward direction. Thus, other components will not be affected by the back-emf. (simplified; Provides an alternate path for inductive current to flow when the primary path is blocked)

DESCRIPTION (Layers)

Each transistor has two P −N junctions where depletion layers form like in diodes. - The first layer emits charge −carriers, which is why it is called the emitter. - The middle layer is called the base or base region of the transistor. Its function is to regulate the emission of the charge −carriers. - The last layer is called the collector. The collector collects the charges.

FLIP-FLOP CIRCUITS General

Flip-Flops are storage devices that have two stable conditions. They are mainly used in digital techniques. The general arrangement consists of two inverters in series (Transistor in emitter arrangement).

Resistive−Capacitive Coupling

Here the alternating current output voltage of the first stage is passed through the coupling capacitor directly on to the next stage. The coupling capacitor has the task of preventing the first stage from causing a shift in the operation point of the second stage. It must be big enough so that its capacitive reactance remains small in comparison to the input resistance of the second stage, even at the lowest frequencies that are to be transmitted.

CHARACTERISTICS AND PROPERTIES General

Here the example of an N − P −N transistor is used to demonstrate how transistors work.

High Power Diode

High power diodes have maximum forward −biased currents of approximately 10 to 1000 amperes.

Disadvantage (DC coupling)

However this circuit has the following disadvantage: the variations in output voltage in the first stage minus only the voltage division ratio are directly passed on to the second stage.

Usage (integrated circuits)

ICs can be found in each and every modern appliance, in analogues as well as in digital ones. Functional blocks can be found in a single IC, requiring only a very small amount of space, i.e. Processors (Computer), Amplifier (Entertainment) or Operational Amplifier (Voltage Regulators or Entertainment).

FEEDBACK General

If a portion of the output voltage of an amplifier is transmitted back to the input terminal, this is called feedback. This feedback can be a desired effect, brought about by the construction of the circuit. However it can also be the negative result of undesired circuit capacitances or defects in insulation ( so −called random feedback). Feedback is of two types: - positive feedback - negative feedback.

clampers (general)

If information is transmitted via radio or if a circuit contains capacitors the DC voltage levels will get lost. A clamper is used to restore such DC voltages.

CASCADES Coupling Possibilities

If the amplifying capacity of a transistor is not enough, several amplifying stages must be connected one after the other. The output voltage of the first amplifying stage is then the input voltage of the next stage. There are two kinds of coupling: the AC coupling and the DC coupling. In an AC coupling , only the alternating current portion of the output voltage of the first stage up to a specific lower threshold frequency is passed on to the next stage. In a direct current coupling the lower frequency threshold is zero which means that the two stages are connected to each other galvanically

Use of Multimeter

If the diode is faulty in the open circuit condition then the reading will be high resistance (or open circuit) in both directions. If it has failed in the short circuit condition (less likely) then it will show low resistance in both directions.

Diodes in Series

If the voltages to be blocked by the diodes exceeds the maximum permissible reverse voltage of a diode several diodes may be connected in series. Usually identical diodes are connected in series as the voltages across the diodes are identical. In this case the total voltage that can be applied is the sum of the individual voltages of the diodes.

Hartley-Oscillator

In case of the Hartley Oscillator a tapped transformer is used. Therefore the name „inductive three point connection".

Meißner-Oscillator

In case of the Meißner Oscillator the feedback is generated via a transformer. A transformer coil together with the capacitor work as resonant circuit.

DC COUPLING General

In the case of direct current voltage amplifiers, neither the transformer coupling nor the R-C coupling can be used because neither type can transmit DC voltage.

Negative Feedback

In the case of negative feedback, the voltage Ug, which is fed back, works against the input voltage and the amplification is reduced .

Positive Feedback

In the case of positive feedback, the voltage Um , which is fed back, supports the input voltage. The amplification increases and the amplifiers tends to oscillate. This is the reason that positive feedback is hardly used except when oscillation is desired.

OSCILLATORS general

In the field of electronic circuits for frequency generation are called generators. They are used for the generation of periodical AC voltage, but no statement concerning the waveform to be generated is made. Common wave forms are: - Square wave voltage - Triangular voltage - Saw-tooth voltage - Sinus-wave voltage Generators that produce more than one form of waves are called waveform generators. Now we will have a look at sinus-wave generators or oscillators.

TESTING OF TRANSISTORS general

In the field the testing options of a transistor are quite limited. The only thing that can be done is a simple functional test of the diodes inside the transistor. Here the same principle applies as when testing a diode. Inside the transistor two diodes are found: - The Base-Collector diode - The Base-Emitter diode So testing a transistor means testing these two diodes. The Ohmmeter in this case is connected to the Base and either to the Collector or the Emitter.

Terminal Markings (Transistors)

In the wiring symbol, the emitter is marked with the arrow. Small transistors have a marking which shows the emitter.

Operation (FLIP-FLOP circuits)

Input E1 is connected to ground for a short time. This causes Transistor T1 to block the current, at its collector the supply voltage Ub is found. It is handed to the base of T2 which then will become fully conductive. The collector voltage across T 2 will go to ZERO. These ZERO volts are supplied to the base of T 1 causing it to toggle to blocking. If 0 V are connected to the base of T 2 the second stable condition is achieved

INTEGRATED CIRCUITS General

Integrated Circuits are arrangements of several electronic components in a common housing.

how do PCB transistors work

It can function as a switch or an amplifier. PCB transistor is a component that can on and off millions of times per second. The current evolution was accelerated when it was utilized as an amplifier. Transistors are the data storage and data transfer components of digital computers.

Voltage Source

Normally only one voltage source is used to supply current to both the base −emitter circuit and the collector −emitter circuit. The voltage for the base is provided by a voltage divider.

SCHOTTKY DIODES (general)

Nowadays Schottky diodes are used in integrated circuits.

Voltage Divider (DC coupling)

Often a direct connection is not possible because the output of the first stage and the input of the second stage have different DC potentials. In this case the coupling is made possible by inserting a voltage divider comprised of resistors between the output terminal of the first stage and the input terminal of the second.

Operating Voltage

Operational amplifiers are usually supplied with both a positive and a negative operating voltage. The positive operating voltage of an operational amplifier lies between +5 volts and +18 volts, the negative voltage between −5 volts and −18 volts. Both operating currents, as is the case for the trimming resistance, are usually not shown in the wiring diagrams. In the schematic symbols for an operational amplifier, just the two input terminals and the output terminal are usually shown

OPERATIONAL AMPLIFIERS General

Operational amplifiers consist of several amplifier stages. The operational amplifier is always a differential amplifier with two inputs and one output. The output stage is usually a push−pull power amplifier. Because operational amplifiers are manufactured using integrated technology, they usually have very small dimensions. Operational amplifiers can amplify both alternating and direct current.

Usage (Operational amplifier)

Operational amplifiers have been used primarily in analogue computers, which is where they get their name from. Today they are used for almost every kind of amplifying task in the analogue area but also in digital technology, for example as digital analogue transducers.

Do electrical components contain PCBs?

Printed circuit boards are used in nearly all electronic products

Rectifier Diode

Rectifier diodes are primarily used for electrical power supply devices. They are used to construct rectifier circuits for small power outputs.

Caution

Remember to switch off the supply power before testing and remove all connections to the base at least to avoid the circuitry around the transistor to influence the measuring.

Shapes

Single crystal semiconductor diodes come in a wide variety of different shapes

Extrinsic Conductivity

Temperature has a much smaller influence on the extrinsic conductivity, however. In the input characteristic field, the rise in temperature pushes the characteristic curves up and higher currents flow at the same voltages. However a temperature rise at a constant current causes a reduction in voltage. As you can see from the above graph, if the base−emitter voltage Ube remains constant and the temperature rises from t1 to t2 the collector current increases by a value of (DELTA) Ic. At the same time, if the collector current remains constant at lc, the base−emitter voltage decreases by (DELTA) Ube. Per temperature increase of one Kelvin, the base emitter voltage UBE drops by 2.2 mV (TK = −2.2mV/K). Of the transistor characteristics, the current amplification factor B is even more dependent on temperature than the base emitter voltage Ube.

Cascade Circuit

The Cascade Circuit is a series connection of several Villard Circuits and works according to their principle. The voltage of one capacitor and the transformer voltage are passed on to the following capacitor. As a matter of principle, any voltage can be created. Just the amount of Villard circuits determines the factor the input voltage will be multiplied with. This will allow voltage tripplers, quadruplers, ... The current carrying capacity however is very low. This circuit is often used in TV sets, computer monitors, and oscilloscopes. (several Villard circuits the voltage of one capacitor and the transformer voltage are passed onto the following capacitor --- current carrying capacity is low used in TVs, monitors, oscilloscopes)

Delon Circuit

The Delon Circuit reminds one of a two-way rectification, but the two half-cycles are not sent to the load together. Instead capacitors are charged and the total of the two capacitor voltages is the new output voltage. The two half waves are added. This circuit is also called voltage doubler. At the airplane it is used in the igniter box. (capacitors are charged, two half cycles added together and the total of two capactior voltage is the new output voltage (doubled) used in aircraft igniter box)

villard circuit

The Villard Circuit is based on the one-way rectifier. In case of a negative half-wave the capacitor C 1 is charged. In case of a positive half-wave the transformer voltage and the C 1 voltage are added . Since diode D 2 is now connected in conducting direction, the capacitor C 2 is charged with the voltage of the transformer + C1. (the capacitor is charged up when the waveform goes negative (through the diode), and releases its charge when the waveform goes positive.)

polarity

The arrow of the wiring symbol shows the direction of the current which flows between base and emitter. N-P-N transistors require the Base voltage and the Collector voltage to be positive in respect to the Emitter. P-N-P transistors require the Base voltage and the Collector voltage to be negative in respect to the Emitter.

Operating Point

The change in collector current due to changes in temperature causes a shift in operating point. This means that the modulation range is narrowed because the positive or the negative half−waves are distorted even by the smallest input voltages if the operating point is no longer in the centre of the average workload. When the ambient temperature is increased, the maximum permissible power load decreases as well, putting the transistor in danger of overheating. For this reason it is necessary to take precautions in the circuitry to stabilize the operating point. In order for a transistor to retain the characteristic properties typical for its characteristic curves and parameters, it is important not to heat it above certain temperature limits. The critical point of the transistor is the junction or barrier layer of the collector base. (see transistor residual currents).

Collector/Emitter Voltage

The collector has a positive voltage Uce as opposed to the emitter so that the collector −base diode is in the blocking direction.

NPN and PNP

The difference between N-P-N and P-N-P transistors is the arrangement of the layers and therefore the direction of the two diodes inside the transistor. - The NPN-transistor has a N-layer, a P-layer and a N-layer. - The PNP-transistor has a P-layer, a N-layer and a P-layer. The basic operation principle is the same to both N-P-N and P-N-P transistors. Due to the direction of the two diodes inside the transistor the polarity of the voltages applied to the terminals is reversed.

External Wiring (Operational amplifier)

The external wiring, which is done in the form of negative feedback, determines how the circuit will function.

Properties (operational amplifier)

The ideal operational amplifier has - an amplification which is nearly infinite - an input resistance which is almost infinite - a very small output resistance - an input voltage of approximately zero volts.

Basic Principle of an Oscillator

The layout of an oscillator is that of an amplifier whose output signal is routed back to the input. A phase shift of 0 degrees or 360 degrees respectively is mandatory, because only then a positive feedback is generated. The amplifier thus operates as oscillator. In the case of common NF-amplifiers one usually tries to inhibit this tendency to oscillate by decreasing the amplification, but most people are familiar with the result: A high pitched whistle is experienced during live events if the microphone is located too close to the amplifiers. This is an acoustic feedback which creates an undesired oscillation of the amplifier.

Threshold Voltage (Schottky diodes)

The main advantage over silicon diodes is the reduced threshold voltage of approximately 0.3 V resulting in faster switching between conducting and non-conducting conditions.

Advantages (integrated circuits)

The major advantage is the very high density of the components, the total arrangement therefore will be very compact. As well they are quite resistant to mechanical stress. ICs are very cheap.

Maximum Temperature

The maximum permissible temperature that the junction can have varies according to the semiconductor material used. For germanium, it is 75 to 90 degrees C and for silicon, it is 150 to 200 degrees C.

Oscillator

The oscillator generates a sinus-shaped output voltage. This can be a sinus without superposition of AC and DC or with superposition (shifted up or down). in this case we are talking about undulated current. The oscillator shown here generates sine waves between 1 kHz and 10 kHz. Oscillators used to be designed with transistors - modern oscillators are ICs which contain all components and whose frequency can be changed via input. Often the wave form is reversible or changeable by means of additional circuits. The basic principle of these IC's is usually an operational amplifier.

output (operational amplifiers)

The output voltage is measured between the output terminal and the common terminal for both operating voltages. When the difference input voltage U1 is positive, a negative output voltage U2 is the result; when there is a negative input voltage U1, then there is a positive output voltage U2.

Transformer Coupling

The primary coil of the transformer creates the load resistance of the first stage. The alternating current for the next stage is passed over the secondary winding. The capacitor C has the task of preventing a short circuit of the upper partial resistance of the base voltage divider as a result of the secondary coil of the transformer. In some rare cases a resistor may be used instead of a capacitor. In this case it is a so-called inductive-resistive coupling. A transformer coupling has the advantage that by properly choosing the ratio between the number of turns in each coil an optimum resistance match can be achieved. However disadvantages abound. Transformers are expensive, they only transform within a specific frequency range and the magnetizing curve of its iron core can lead to additional distortions of form.

Problems (low frequency power amplifiers)

The problems that occur with a 𝗽𝗼𝘄𝗲𝗿 𝗮𝗺𝗽𝗹𝗶𝗳𝗶𝗲𝗿 are in the areas of - power output - efficiency - distortion

Examples

The schematics shown in figure 2 is a typical emitter arrangement which in digital techniques is frequently used as inverter. The switching of a light barrier with a switching transistor is shown in figure 3. When light strikes the photocell, the resistance value of Rx drops suddenly. The voltage at the base of the transistor rises. The transistor is put into a low resistance state. The collector current Ic flows through the relay and it is energized. When the beam of light is interrupted, Rx becomes highly resistive (about 1 Mega-Ohm). The transistor blocks: The relay becomes de-energized.

Direct Connection (DC coupling)

The simplest DC coupling is achieved by directly connecting the output terminal of the first stage with the input terminal of the second. However this is only possible when the output of the first stage has the same direct current potential as the input of the second stage.

Disadvantages (integrated circuits)

The small housing and therefore the small surface is a disadvantage because some additional cooling might be required. A heat sink or fan must be attached then. Another disadvantage is that ICs can not be repaired, a defective IC must always be replaced.

Terminals

The terminals are called collector (C), base (B) and emitter (E). In many transistor contructions the collector is connected to the transistor housing.

circuit (the transistor as a switch)

The transistor in its switching function is often used in emitter circuits. Here the input and output terminals behave in the opposite manner: If there is no voltage at the base (input terminal), the transistor blocks and lets no current through. Then, because of the high resistance, no current is flowing so, in accordance with Ohm's Law, there is no voltage across the resistor, therefore full voltage is at the output terminal. When the voltage at the input terminal increases to a level greater than 0.7 volts, the transistor switches to conducting, therefore at the output terminal almost no voltage can be measured.

Wiring Symbol (Transistors)

The wiring symbols for NPN-transistors and PNP-transistors are shown below. The circles are often omitted. The terminal with an arrow is named emitter. If the arrow points outside the transistor, it is a NPN transistor.

how is the Z diode used

The zener diode is used as a Shunt voltage regulator for regulating voltage across small loads. The Zener diode is connected parallel to the load to make it reverse bias, and once the Zener diode exceeds knee voltage, the voltage across the load will become constant.

what is the Rectifier Diode's maximum forward?

Their maximum forward −biased currents can be as much as 10 amperes.

AC COUPLING General

There are several ways of passing the alternating current output voltage of one stage on to the next. The most common ways of doing this are: - transformer coupling - resistance−capacitance or RC coupling.

how are High Power Diodes used?

They are used in rectifier circuits for large power outputs.

what are schottky diodes and how do they work?

They contain metal-semiconductor junctions that have quite the same properties as P-N junctions. As an example aluminium and N-doped silicon are joined. The Aluminium will act as an Anode (P-doped material). In contrast to that junctions between aluminium and highly doped N-silicon or aluminium and P-doped silicon will be depletion area free joints. Though no extra symbol is available for Schottky diodes many companies (manufacturers) use the symbol below.

inputs (operational amplifiers)

They have two input terminals. The inverting input is usually designated with a minus sign and the non−inverting input with a plus sign.

Z-Diode

This disadvantage can be removed if, instead of R 2 a Z −diode is used. The voltage drop at a Z −diode is nearly constant in the breakdown area; in this way the output variations of the first stage are passed on unchanged to the input terminal of the second stage.

Usage (the transistor as a switch)

Transistor switching stages are commonly used for computers, for electronic clocks, electronic counters and for control circuits of all kinds. They can be found, for example, in the ignition systems and directional lights of motor vehicles.

THE TRANSISTOR AS A SWITCH General

Transistor switching stages are used everywhere where small or medium amounts of power must be switched quickly with solid state technology. The resistance levels of the transistors between the emitter and the collector are controlled between resistance as high as possible and resistance as low as possible. In switching stages, transistors are only operated in the states "high resistance" = "switch open" and "low resistance" = "switch closed"

examples of Diodes in Series

Two diodes with a maximum reverse voltage of 60 V are connected in series. - The voltage applied in reverse direction is 100 V. - The individual voltages across the diodes are 50 V each. - The maximum permissible reverse voltage is 120 V.

Single−ended Amplifier A−Output Stage

Up to now, in all of the amplifiers that we have looked at, the operating point was put in centre of the load line so that both half−waves can be equally amplified. This position of the operating point is called A−operation Larger modulation is not possible. Otherwise the curve of the input characteristic and the collector−emitter saturation voltage will create strong distortions. In addition, because the alternating current input voltage is missing, a large amount of power is transformed into heat energy in the transistor so that the efficiency becomes low ( η max < 33%). In power amplifiers A−operation is used only in the case of small power outputs of up to a few watts. Single−ended amplifier output stages can only function in A−operation mode because the transistor must then amplify both of the half−waves.

Clampers

Used to add a DC voltage level to an AC input signal

Elements (integrated circuits)

Usually the following components are integrated in ICs: - Semiconductors (Transistors, Diodes) - Resistors - Capacitors Inductors usually can not be integrated due to their large space requirements

Diode Test Position

When a multimeter is set to the diode test position it will supply a voltage sufficient to forward and reverse bias the diode. This voltage will be approximately 2.5 −3.5 volts. A serviceable diode will show around 0.7 volts on the multimeter when tested in the forward bias direction and will show the internal voltage of the meter when tested in reverse bias. If a diode has failed open circuit, it will show the internal voltage of the meter in both forward and reverse bias. If it has failed in the short circuit condition it will show zero (or nearly zero) in both directions.

Intrinsic Conductivity

When the temperature rises, additional charge−carrier pairs become free in a semiconductor. This increases its intrinsic conductivity. As a result, the temperature flow has its greatest effect on its residual currents. When the temperature of the junction is raised from 25 degrees to 150 degrees Centigrade, the residual current in a silicon transistor becomes 2000 times higher.

LOW FREQUENCY POWER AMPLIFIERS General

While it is important in the case of preamplifiers to adapt the amplifier input to the signal source and to amplify small voltages, giving the frequency response of the amplifier the right shape, the main focus of a low frequency power amplifier is to produce the AC power necessary for the loudspeaker. On the one hand, a transistor which is to transmit the largest possible power must be modulated to its maximum. This is difficult because the characteristics for transistors are not completely linear so distortions can occur. On the other hand, the efficiency, that is the ratio of alternating current power transmitted to the amount of direct current power received, should be as high as possible. Otherwise, especially in the case of large power outputs, operating costs can be high.

z diode (General)

Z-Diodes are silicon diodes with a specifically defined steep breakdown in the reverse biased direction. When the voltage is changed minimally, the current changes radically and the diode remains intact. Of course the maximum power dissipation level must not be exceeded.

Curve (Z-diode)

Z-diodes show a very steep curve. This means that the dynamic resistance is especially small in the breakdown area.

Application (z-diode)

Z−diodes are mainly used to regulate electrical voltage. In the entry area is the input voltage U E; at the load resistance R 2 which is connected in parallel to the Z −diode is the regulated output voltage U A = Uz. The difference between the input voltage U E and the output voltage U z is purged at series resistor R 1 .

testing of diodes: General

a diode will show a very high resistance (or open circuit) if wired in the reverse bias direction, and a very low resistance when wired in the forward bias direction. These two situations can be measured using a 𝙢𝙪𝙡𝙩𝙞𝙢𝙚𝙩𝙚𝙧.

what is a diode?

a semiconductor device that essentially acts as a one-way switch for current

what is the function of transistors

amplifying and switching electrical signals

whats the positive end of a diode?

anode

what is the Microdiodes maximum forward?

biased current lies mostly far below one ampere. they have different names according to how they are constructed: - Junction diodes - Point-contact diodes - or planar diodes

what is the negative end of a diode?

cathode

Decoupling

diodes can be used as a decoupling network or to decouple electrical components. The goal is to control both lamps with switch S1, but only lamp L2 with switch S2.

diodes in parallel (simplified)

forward current is divided between them

Diodes in Series (simplified)

forward current will be the same

microdiodes

mainly used in communication technology

what are the three different types of single crystal semiconductor diodes?

microdiodes rectifier diodes high power diodes.