SEMICONDUCTORSLECTURE 16 TRANSISTORS

TRANSISTORS P.48

First transistor 1947

First commercial transistorLECTURE#16

First computer to use these transistors

YOU TUBE: HOW TRANSISTORS WORK

http://www.youtube.com/watch?v=ZaBLiciesOU

BIPOLAR TRANSISTORS ARE SEMICONDUCTOR DEVICES WITH 3 LEADS, CALLED THE EMITTER, BASE AND COLLECTOR. THE TRANSISTOR ISBASICALLY 2 P-N JUNCTIONS BUTTED UP AGAINSTEACH OTHER.A SMALL VOTLAGE OR CURRENT AT ONE LEAD CAN CONTROL A MUCH LARGER VOLTAGE OR CURRENT AT THE OTHER TWO.TRNSISITORS CAN BE USED AS AMPLIFERS ORAS SWITCHES.

ACTS LIKE A 3 LAYER SANDWICH

THIS LAYERING CAN BE PNP OR NPN

THE MIDDLE LAYER (BASE) CAN ACT AS A GATE CONTROLING THECURRENT THRU THE 3 LAYERS. THE BASE LAYER IS THIN AND HAS LESS DOPING ATOMS THEN THE EMITTER AND COLLECTOR.A SMALL BASE CURRENT WILL CAUSE A LARGER EMITTER-COLLECTORCURRENT TO FLOW.

http://www.youtube.com/watch?v=RdYHljZi7ysHow the first transistor worked

INPORTANT POINTS TO REMENBER ABOUT TRANSISTOROPERATION.1. THE BASE-EMITTER JUNCTION WILL NOT CONDUCT UNTIL THE FORWARD VOLTAGE EXCEEDS 0.6VDC2. TOO MUCH HEAT CAN DESTROY OR CAUSE A TRANSISTOR NOT TO OPERATE CORRECTLY.3. TOO MUCH VOLTAGE OR CURRENT WILL DESTROY THE CHIP INSIDE THE TRANSISTOR OR CAUSE THE LEADS ATTACHED TO IT TO MELT.

TYPES OF TRANSISTORS

YOU TUBE: MAKE PRESENTS THE TRANSISTOR http://www.youtube.com/watch?v=-td7YT-Pums

HIGH FREQUENCY TRANSISTOR

http://www.youtube.com/watch?v=HTQQnl1pArkHow to use transistor as switch.mp4

WHEN THE BASE IS GROUNDED (0V)NO CURRENT FLOWS FROM THE EMITTER TO THE COLLECTOR. IF ABOUT 0.6V IS APPILED TO THE BASE THE TRANSISTOR IS SAID TO BE FOWARD BAISED, CURRENT WILL FLOW FROM THE EMITTER TO THE COLLECTOR (TRANSISTOR IS ON). TRANSISTOR IS OPERATING AS A SWITCH.

CALLED COMMON EMITTER CIRCUIT SINCE BOTH EMITTERS ARE GROUNDED

TO-3 OPENED

2N3055

2N3055 IS COMMONLY USED IN POWER SUPPLIES

YOU TUBE: Field Effect Transistors, Part 1,START AT 7:00MIN http://www.youtube.com/watch?v=CLLcRRBph90

Bias arrangement for an N-channel JFET JFET Channel Pinched-off

n-channel metal-oxide semiconductor

MOSFETS ARE USED IN MICROPROCESSORS AND MEMORY CIRUITS DUE TOTHEIR EASE OF MANUFACTURE, SMALL SIZE, LOW POWER USE, AND HIGH OPERATINGSPEED. SUBJECT TO ESD DAMAGE. GENERALLY CAN’T HANDLE HIGH POWER LEVELS

MOSFETS: METAL OXIDE SEMICONDUCTORS-FETS

http://www.youtube.com/watch?NR=1&feature=endscreen&v=x7OnX6e5pvcThe MOSFET

How a CMOS Chip Works (digital camera) http://www.youtube.com/watch?v=HEVEGVV4EHk

YOU TUBE: transistor/mosfet tutorial

http://www.youtube.com/watch?v=Te5YYVZiOKs http://www.youtube.com/watch?v=JCPXckfT-6g

Exploding electronic components in HD

GATE HAS NO ELECTRICAL CONTACT BETWEENTHE SOURCE AND THE GATE

(ACTS AS AN INSULATOR)

The Field Effect Transistor Family-tree

                                             

                                

ESD PRECAUTONS

YOU TUBE: ESD PREVENTION MEASURES

http://www.youtube.com/watch?v=QNahnyx9OWQ

2 gates

Anode

Cathode

Thyristor with voltageRange from 400 to 1kvCurrent 16A to600A

thyristor: n-p-n-p-n-p transistors

DIFFERENT PACKAGE CASES FOR THYRISTORS

http://www.youtube.com/watch?v=TFuiqDbkAX0

CCEA AS Technology and Design Unit1 - The Thyristor

This circuit detects light when light is present in a room.  With no light, the photo-transistor does not conduct. When light is present, the photo-transistor conducts and the bell is activated. Turning off the light will not stop the alarm. The alarm is turned off via S1.

Animation of SCR Operation

Alarm device using a thyristor and a photo-transistor

SCR

DIFFERENT PACKAGE CASES FOR SCR’S

600V,1000A SCR

SCR / Thyristor module, 6500V, 1,500A for 50us pulse (hockey puck)

TRIAC IS THE SAME AS 2 REVERSE PARALLEL SCR’s

A diac is a diode AC switch which acts as a bidirectional semiconductor switch.

A diac is a full-wave or bi-directional semiconductor switch that can be turned on in both forward and reverse polarities. Indeed the name diac means diode AC switch.

Symbols and pin placements for: a - thyristor, b - triac, c - diac

THYRISTORS

TRIACS

DIACS

K: Cathode

TRIAC

TRIACs are like 2 parallel SCRsThey are thus able to switch both sides of an  AC sine waveThey are often switched using DIACSThey can be used to control AC loads by switch action or the progressive trimming of the sine waveThrough the use of optical coupling they can be safely interfaced with computer control circuits!

 

The diac is widely used to assist even triggering of a triac when used in AC switches. Diacs are mainly used in dimmer applications and also in starter circuits for florescent lamps.

                                                                                                                        

A pushbutton switch controls the flow of current in a load

                                                                                                                                        

                                            Current injected into the GATE controls the TRIACA TRIAC switch controls the current through a load

Because it can be controlled to trigger at different voltage points on the sine wave it can be used to effectively control the RMS power delivered to the load rather just crude on / off.

It's like a switch that can turn on and off at different times on the sine wave.

HOW AC DIMMER SWITCHES WORK

                                                                                                                 

                                                          The TRIAC is a gate controlled switch.

 

                                                                                                                 

                                                                   Low voltage logic circuits are fragile and expensive they should be electrically isolated from the high voltage TRIAC circuit using an Optocoupler  module chip

RMS power and voltage to the load are controlled by trimming of the AC sine wave.

The TRIAC effectively chops the AC sine wave and reduces the amount of current reaching the light bulb.

A TRIAC dimmer chops both the leading and trailing edge of the AC cycle.

The variable resistor sets the point on the sine wave where trimming occurs effectively dimming or illuminating the light.The capacitor and inductor attempt to minimize interference that is generated by the snapping effect of the TRIAC on the sine wave  like striking a bell ringing, harmonics  (some RF even) are created in the circuit that can interfere with other devices.

http://www.youtube.com/watch?v=tyQ-BM7sXy0The TRIAC and the Light Dimmer Circuit

HARMONICS

Filament Light Dimmer Circuit

Filament Light Dimmer CircuitThis simple triac dimmer can be used to control incandescent filament lamps up to 200W. The circuit operates on the phase-control principle.

PARTS LIST

R1 10kΩ 0.5W

R2 100Ω 0.5W

VR1 500kΩ Potentiometer

C1 330n (0.33µF)

C2 100n (0.1µF)

D1 DB3 Diac

Q1 BT136 Triac

L1 Filament Light

The main control is provided by VR1. This determines the rate at which C1 charges and hence the point along the AC waveform at which the voltage on C2 reaches the breakdown voltage  of the diac (D1), which is when the triac is triggered.

This is a real world dimmer equivalent of the circuit on the last slideNote the inductor and the capacitor are used for phase shifting and noise filtering.

Have you ever noticed the 60 Hz ringing sound that comes from light dimmers and sometimes the filament of incandescent lights that are dimmer controlled? It is the result of the chopping of the sine wave feeding the light.

Typical home light dimmer uses a TRIAC

In a light dimmer switch, resistors rapidly shut the light circuit off and on to reduce the total amount of energy flowing through the circuit. The switching cycle is built around the fluctuation of alternating current (AC). AC current has varying voltage polarity -- in a sine wave, it fluctuates from a positive voltage to a negative voltage. To put it another way, the moving charge that makes up AC current is constantly changing direction. In the United States, it goes through one cycle 60 times a second. The diagram below shows this sixtieth-of-a-second cycle

A modern dimmer switch "chops up" the sine wave. It automatically shuts the light bulb circuit off every time the current reverses direction -- that is, whenever there is zero voltage running through the circuit. This happens twice per cycle, or 120 times a second. It turns the light circuit back on when the voltage climbs back up to a certain level, as seen in the diagram below

This "turn-on value" is based on the position of the dimmer switch's knob or slider. If the dimmer is turned to a brighter setting, it will switch on very quickly after cutting off. The circuit is turned on for most of the cycle, so it supplies more energy per second to the light bulb. If the dimmer is set for lower light, it will wait until later in the cycle to turn back on.

Illuminance Example

0.002 lux Moonless clear night sky

0.2 lux Design minimum for emergency lighting (AS2293).

0.27 - 1 lux Full moon on a clear night

3.4 lux Dark limit of civil twilight under a clear sky

50 lux Family living room

80 lux Hallway/toilet

100 lux Very dark overcast day

300 - 500 lux Sunrise or sunset on a clear day. Well-lit office area.

1,000 lux Overcast day; typical TV studio lighting

10,000 - 25,000 lux Full daylight (not direct sun)

32,000 - 130,000 lux Direct sunlight

LUX, Unit of illumination in the International System of Units (SI). One lux (Latin for “light”) is the amount of illumination provided when one lumen is evenly distributed over an area of one square meter.

Aka: Light Dependant Resistor (LDR)

http://www.youtube.com/watch?v=PecciHMth4gTISHITU LDR (Light Dependent Resistance) with 555 Timer

Stove top burner LDR detector

STOVE TOP BURNER LDR DETECTOR

DETECTS SPECIFIC FREQUENCY OF LIGHT(FROM BURNING GAS) IF NOT PRESENT,GAS IS SHUT 0FF

Online Tutorial On Types Of Transducers http://www.youtube.com/watch?v=A7_OgrlynRI

PHOTOTRANSISTOR USED TO DETECT THE SPEED OF A ROTATING DISC

Website for this imagehackedgadget.tistory.com

A Simple and Cheap Dark-Detecting LED Circuit

LTR-4206E phototransistor

4N35 - Optocoupler Phototransistor

Phototriacs for Consumer Applications Webinar http://www.youtube.com/watch?v=cXvyNSzhWlw

http://www.youtube.com/watch?v=GSzVs7_aW-YVoltage regulator tutorial & USB gadget charger circuit