Nary a problem!

Somehow or other, I managed to repair him.

Semiconductors are substances whose electrical characteristics change due to the effects of heat, light, or electricity.

A semiconductor that is made up of two or more elements such as gallium arsenide (GaAs) is called a compound semiconductor.

There are also cases in which a small amount of an impurity is mixed with the silicon (Si) or germanium (Ge). This process is called doping, and the result is called an extrinsic semiconductor. A semiconductor with no impurity mixed in is called an intrinsic semiconductor.

The purity of this refined silicon is 99.999999999 percent, which is sometimes referred to as eleven-nine.

A silicon atom has four valence electrons in its outermost shell. These atoms jointly contribute four electrons to form a firm, regular crystal. A silicon crystal does not have any electrons that can freely move around, so electricity will hardly pass through it.

If an element with five valence electrons, like phosphorus (P), is mixed in with a silicon crystal the phosphorus and silicon bond, and one valence electron escapes. This causes the electrical conductivity of this semiconductor to increase. This semiconductor is called an n-type semiconductor because the electron, which has a negative electrical property, becomes a carrier of electricity.

Now, let's say we mixed in a little of the element boron (B), which has three valence electrons. The boron and silicon bond, but there is an empty seat left in the space that doesn't have an electron. This empty seat is called a hole. Holes are places electrons are vacant in covalent bonds. This kind of semiconductor is called a p-type semiconductor because the hole, which has a positive electrical property, becomes a carrier of electricity.

The substance formed by mixing an element such as phosphorus or boron into a pure silicon crystal is called an extrinsic semiconductor.

If a p-type semiconductor and n-type semiconductor are combined to form a structure called a p-n junction, a semiconductor device called a diode is created. The electrode of the p-type semiconductor side is called the anode, and the electrode of the n-type semiconductor side is called the cathode.

A diode has a property called rectification, which allows current to flow only in one direction.

If we compare it with water, it's similar to the action of a valve installed in a water pipe.

Since the luminescence of light-emitting diodes (LED) does not involve heat, they are energy efficient and have a long lifetime.

Transistors are semiconductor devices that amplify signals or act as switches by controlling the current or the voltage that is applied to an electrode. Two types of transistors are NPN and PNP transistors. They have three electrodes referred to as B (base), C (collector), and E (emitter).

The current that flows from the base to the emitter is called the base current. When the base current flows, current will also flow from the collector to the emitter. This current is called the collector current. The collector current will change significantly in response to a slight change in the base current.

We can illustrate this concept in terms of water like this.

Unlike a regular switch, it has no physical contact, so it doesn't wear out and is less likely to fail. Also, since it can be turned on and off rapidly, control can be fine tuned.

It really has some great advantages!

An integrated circuit (IC) contains an extremely large number of elements such as transistors, diodes, resistors, and capacitors - these complicated circuits can perform digital logic.

Your studies are over! Thank you for all your hard work!

No way! It's you who deserves all the thanks.

I learned a lot by teaching you.

When a single diode is connected to an AC power supply, current flows to the load for only one direction of the AC power supply due to rectification. Rectification that only allows a half-cycle of the alternating current to flow is called half-wave rectification.

When four diodes are arranged in a bridge configuration and an AC power supply is connected, the current of the entire cycle becomes positive and flows to the load. This kind of rectification is called full-wave rectification, and diodes that are connected in this way are called a diode bridge.

Although this kind of full-wave rectification is more efficient than half-wave rectification, the waveform exhibits large pulsations. However, if an electrolytic capacitor is connected to the output, the charging and discharging of the capacitor can change the pulsations in the waveform into a flat, smooth direct current. A capacitor that is used to change a pulsating flow to a flat waveform in this way is called a smoothing capacitor.

If a reverse-direction voltage is applied to a Zener diode (or constant-voltage diode) and the value of the voltage is steadily increased, current will flow once a certain voltage is reached. This phenomenon is called breakdown, and when the circuit voltage rises more than necessary, current can flow from the cathode to the anode to suppress the rise in voltage.

A transistor is a semiconductor device that amplifies signals or acts as a switch by controlling the current or the voltage that is applied to an electrode.

When a large amount of electric power is controlled by a transistor that is used as a switch, the transistor is called a power transistor. Generally, an NPN-type transistor is used in this way.

A transistor in which the collector current is controlled by the change of current that is input to the base is called a bipolar transistor (junction transistor). In contrast, a transistor that is controlled by changing the voltage that is input, rather than the current, is called a field-effect transistor (FET).  A field-effect transistor has three terminals that are referred to as G (gate), D (drain), and S (source), which correspond to the base, collector, and emitter of a bipolar transistor, respectively.

A device that uses a diode to convert alternating current to direct current is called a converter, and a device that converts direct current to alternating current is called an inverter.

A temperature sensor is a device that opens or closes a contact or varies electrical resistance according to the temperature it detects.

A bi-metal thermostat is the simplest temperature sensor. It uses a bi-metal strip consisting of two types of metal with different thermal expansion rates, which curves in response to a temperature change.

A thermistor is a temperature sensor whose electrical resistance varies according to a temperature change. Thermistors are classified into positive temperature coefficient (PTC) thermistors, those whose resistance value rises when the temperature rises, and negative temperature coefficient (NTC) thermistors, those whose resistance value falls when the temperature rises.

The phenomenon in which a substance such as a metal absorbs light energy and emits electrons as a result is called the photoelectric effect.

The phenomenon that describes how voltage appears at the junction of a semiconductor due to the photoelectric effect is called the photovoltaic effect.

A solar cell generates an electromotive force when light energy strikes the p-n junction surface.

The effect in which a carrier of electricity such as an electron is generated by the photoelectic effect, thus causing the internal resistance value of a substance to change, is called photoconductivity. A cadmium sulphide (CdS) cell is a solar cell that functions using photoconductivity.

A photodiode is a semiconductor device in which current flows from the cathode to the anode due to the photovoltaic effect when light or infrared rays are received.

A photodiode combined with a transistor is called a phototransistor.

Thanks to you, I had no problem graduating.

Now we can be lab partners!!