Rectifiers and Battery Chargers - Part A Flashcards
How do you find the instantaneous value of an AC sine wave?
you take the maximum or peak value of that sine wave and multiply it by the “sin” of the angle you are trying to find the voltage at Vi = Vmax X sin (angle)
How do you find the Effective or RMS value of an AC sine wave?
you multiply the maximum or peak value of that sine wave by 0.707…or… divide by the square route of 2 Veff = Vmax X 0.707
What two things does an Oscilloscope display on a graph?
Voltage and Time
How many Valence electrons do Conductors have?
1-3
How many Valence electrons do Insulators have
5-8
How many Valence electrons do Semiconductors have?
4
What is “doping” and how does it work?
The process of introducing impurities into a pure intrinsic material Only about one atom of impurity is introduced for every twelve million atoms of pure intrinsic material, and this is enough to reduce the resistance of the material The result is “Extrinsic Material” which is either N-type or P-type
What is a Semiconductor?
Semiconductor’s are neither good conductors or good insulators. The possess four valence electrons are referred to as “tetravalent elements”
What are the two most common elements used in Semiconductor devices?
Silicon (Si) is the most common Germanium (Ge) has also been used
What happens when you dope Silicon with Pentavalent atoms/materials?
Doping Silicon with Pentavalent materials creates N-type semiconductor material, which, means there is a loosely bonded free electron available as a charge carrier
What is a Pentavalent atom or material? And what are some examples of these materials?
Pentavalent atoms or materials have five valence electrons Some examples are arsenic, phosphorous, and antimony
What happens when you dope Silicon with Trivalent atoms/materials?
Doping Silicon with Trivalent materials makes P-type semiconductor material, which means there is a deficiency of one electron which results in a hole in the crystal lattice structure of the material
What is a Trivalent atoms/material? And what are some examples of these materials?
Trivalent atoms/materials have three valence electrons Some examples are Boron, Aluminum, and Indium
What are the majority charge carriers in P-type semiconductor material?
The majority charge carriers in P-type semiconductor material are holes
What are the majority charge carriers in N-type semiconductor material?
The majority charge carriers in N-type semiconductor material are electrons
What are Light-Dependent Resistors (LDR) or photoresistors?
They are photoconductive cells(photocells), which means when they are exposed to light some of their electrons break their covalent bonds, which reduces their resistance These semiconductor devices are composed of materials like lead-sulphide, indium-antimonide, and cadmium-sulphide.
What is a Diode?
A Diode is a basic semiconductor device composed of a PN Junction It allows current to flow in one direction and prevents current flow in the opposite direction It behaves like a switch The lead attached to the P-type material is called the Anode(A) and the lead attached to the N-type material is called the Cathode(K)
What is a Metal-Oxide Varistor(MOV)?
A Metal-Oxide Varistor is a common type of surge suppressor
It filters out voltage spikes that occur on an AC supply
What is a Forward-Biased Diode?
- A diode only allows current to flow if the Anode(A) is positive with respect to the Cathode(K) with sufficient voltage
- Ignoring the Barrier Potential, a forward-biased diode behaves like a closed switch
- When a voltage of the correct polarity is gradually increased from zero volts, the free electrons in the N region, repelled by the negative cathode lead, start to move toward the PN junction. At the same time, the holes in the P-type material are drive away from the positive Anode lead toward the PN junction. Because the depletion region of the PN junction no longer has charge carriers it presents a barrier to current flow
- A minimum amount of applied voltage must be applied to the PN junction. This allows the charge carriers to be pushed across the depletion region and current to flow. This applied voltage is called the “Barrier Potential”
- When the applied voltage equals the Barrier Potential, the depletion region is overcome and current flows from the Anode(A) to the Cathode(K)
- At room temperature, the Barrier Potential for a Silicon(Si) PN junction is approximately 0.7V
- At room temperature, the Barrier Potential for a Germanium(Ge) PN Junction is approximately 0.3V
What is Barrier Potential?
- a Diode will not allow current to flow if the Anode(A) is negative with respect to the Cathode(K), this is called reverse bias
- When an external voltage is applied where the Cathode(K) is positive with respect to the Anode(A), the diode is reverse biased. Under this condition the electrons in the N-type material are attracted away from the PN junction towards the positive terminal, while the holes in the P-type material are attracted to the negative terminal. The charge carriers are attracted to both ends of the diode and almost no current flows through the Diode
- There is a small amount of reverse current referred to as “leakage current”, but this is insignificant in most cases
- A Reverse-Biased Diode can be thought of as an open switch
- The ideal reverse resistance of a Silicon diode is infinity; in more practical terms it is approximately 30 Mega Ohms
What is the Forward Bias Limit of a Diode?
- It is the rated current or maximum continuous forward current of the diode - If(max)
- If the current flowing through the diode exceeds the the forward bias limit of that diode, it can cause overheating which may destroy the diode
What is the Reverse Bias Limit of a Diode?
- It is the maximum reverse voltage that can be appled to the diode
- this limit may also be called the “Voltage Repetitive Reverse Maximum”(Vrrm), “Peak Inverse Voltage”(PIV), or “Peak Reverse Voltage”(PRV)
- “Breakdown Voltage” or “Avalanche Voltage” are a voltage above the Reverse Bias Limit which causes the diode to breakdown and allow high values of reverse current to flow and destroy the diode. This is called the “Avalanche Current”
What is the “Breakdown Voltage” or “Avalanche Voltage” of a Diode?
- Voltages above the safe maximum or Reverse Bias Limit, that cause the diode to breakdown and allow high reverse currents to flow, which destroy the diode. This high current is called the “Avalanche Current”
What is the rating of a Low Current Diode?
A typical low-current diode has a current rating of 3A or less
