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Transcript
SEMICONDUCTORS LECTURE 16 TRANSISTORS TRANSISTORS P.48 First transistor 1947 LECTURE#16 First commercial transistor First computer to use these transistors BIPOLAR TRANSISTORS ARE SEMICONDUCTOR DEVICES WITH 3 LEADS, CALLED THE EMITTER, BASE AND COLLECTOR. THE TRANSISTOR IS BASICALLY 2 P-N JUNCTIONS BUTTED UP AGAINST EACH 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 OR AS SWITCHES. ACTS LIKE A 3 LAYER SANDWICH YOU TUBE: HOW TRANSISTORS WORK http://www.youtube.com/watch?v=ZaBLiciesOU THIS LAYERING CAN BE PNP OR NPN THE MIDDLE LAYER (BASE) CAN ACT AS A GATE CONTROLING THE CURRENT 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-COLLECTOR CURRENT TO FLOW. INPORTANT POINTS TO REMENBER ABOUT TRANSISTOR OPERATION. 1. THE BASE-EMITTER JUNCTION WILL NOT CONDUCT UNTIL THE FORWARD VOLTAGE EXCEEDS 0.6VDC 2. 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. How the first transistor worked http://www.youtube.com/watch?v=RdYHljZi7ys TYPES OF TRANSISTORS YOU TUBE: MAKE PRESENTS THE TRANSISTOR http://www.youtube.com/watch?v=-td7YT-Pums HIGH FREQUENCY TRANSISTOR 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. How to use transistor as switch.mp4 http://www.youtube.com/watch?v=HTQQnl1pArk CALLED COMMON EMITTER CIRCUIT SINCE BOTH EMITTERS ARE GROUNDED 2 N 3 0 5 5 TO-3 OPENED 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 JFET Channel Pinched-off Bias arrangement for an N-channel JFET MOSFETS: METAL OXIDE SEMICONDUCTORS-FETS MOSFETS ARE USED IN MICROPROCESSORS AND MEMORY CIRUITS DUE TO THEIR EASE OF MANUFACTURE, SMALL SIZE, LOW POWER USE, AND HIGH OPERATING SPEED. SUBJECT TO ESD DAMAGE. GENERALLY CAN’T HANDLE HIGH POWER LEVELS n-channel metal-oxide semiconductor The MOSFET How a CMOS Chip Works (digital camera) http://www.youtube.com/watch?NR=1&feature=endscreen&v=x7OnX6e5pvc http://www.youtube.com/watch?v=HEVEGVV4EHk (ACTS AS AN INSULATOR) GATE HAS NO ELECTRICAL CONTACT BETWEEN THE SOURCE AND THE GATE YOU TUBE: transistor/mosfet tutorial http://www.youtube.com/watch?v=Te5YYVZiOKs Exploding electronic components in HD http://www.youtube.com/watch?v=JCPXckfT-6g The Field Effect Transistor Family-tree ESD PRECAUTONS YOU TUBE: ESD PREVENTION MEASURES http://www.youtube.com/watch?v=QNahnyx9OWQ 2 gates Thyristor with voltage Range from 400 to 1kv Current 16A to600A Cathode Anode thyristor: n-p-n-p-n-p transistors DIFFERENT PACKAGE CASES FOR THYRISTORS CCEA AS Technology and Design Unit1 - The Thyristor http://www.youtube.com/watch?v=TFuiqDbkAX0 This circuit detects light when light is present in a room. With no light, the phototransistor 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. Alarm device using a thyristor and a photo-transistor Animation of SCR Operation SCR DIFFERENT PACKAGE CASES FOR SCR’S 600V,1000A SCR SCR / Thyristor module, 6500V, 1,500A for 50us pulse (hockey puck) A diac is a diode AC switch which acts as a bidirectional semiconductor switch. TRIAC IS THE SAME AS 2 REVERSE PARALLEL SCR’s 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 K: Cathode TRIACS DIACS TRIAC 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. TRIACs are like 2 parallel SCRs They are thus able to switch both sides of an AC sine wave They are often switched using DIACS They can be used to control AC loads by switch action or the progressive trimming of the sine wave Through the use of optical coupling they can be safely interfaced with computer control circuits! A pushbutton switch controls the flow of current in a load HOW AC DIMMER SWITCHES WORK Current injected into the GATE controls the TRIAC A 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. 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. The TRIAC and the Light Dimmer Circuit http://www.youtube.com/watch?v=tyQ-BM7sXy0 HARMONICS Filament Light Dimmer Circuit PARTS LIST Filament Light Dimmer Circuit This simple triac dimmer can be used to control incandescent filament lamps up to 200W. The circuit operates on the phase-control principle. R1 10kΩ 0.5W R2 100Ω 0.5W VR1 C1 500kΩ Potentiometer The main control is provided by VR1. This determines the rate at which C1 charges and hence the point along the AC 330n (0.33µF) C2 100n (0.1µF) D1 DB3 Diac Q1 BT136 Triac L1 Filament Light waveform at which the voltage on C2 reaches the breakdown voltage of the diac (D1), which is when the triac is triggered. Typical home light dimmer uses a TRIAC This is a real world dimmer equivalent of the circuit on the last slide Note 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. 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. 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. 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 Aka: Light Dependant Resistor (LDR) TISHITU LDR (Light Dependent Resistance) with 555 Timer http://www.youtube.com/watch?v=PecciHMth4g 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 image hackedgadget.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 Voltage regulator tutorial & USB gadget charger circuit http://www.youtube.com/watch?v=GSzVs7_aW-Y