PETER PAZMANY CATHOLIC UNIVERSITY SEMMELWEIS UNIVERSITY Development of Complex Curricula for Molecular Bionics and Infobionics Programs within a consortial* framework** Consortium leader PETER PAZMANY CATHOLIC UNIVERSITY Consortium members SEMMELWEIS UNIVERSITY, DIALOG CAMPUS PUBLISHER The Project has been realised with the support of the European Union and has been co-financed by the European Social Fund *** **Molekuláris bionika és Infobionika Szakok tananyagának komplex fejlesztése konzorciumi keretben ***A projekt az Európai Unió támogatásával, az Európai Szociális Alap társfinanszírozásával valósul meg. 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 1
Peter Pazmany Catholic University Faculty of Information Technology www.itk.ppke.hu ELECTRICAL MEASUREMENTS (Elektronikai alapmérések) Semiconductors basics: diodes and transistors Félvezető alapismeretek: a dióda és a tranzisztor Dr. Oláh András 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 2
Lecture 6 review Introduction to Circuit Theory Defnitions of corresponding quantities History of Circuit Theory Definition of elements The Kirchhoff laws Classificition of elements Linear resistive circuits Thevenin and Norton equivalent circuits System and Networks Linear dynamic circuits 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 3
Outline Nonlinear resitive components Diode: p-n junction Actuel diode characterestics and used models Nonlinear element in linear resistive network Load-line analysis (graphical method) Types and applications of diodes Field Effect Transistor (FET) JFET and MOSFET operating characteristics 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 4
Nonlinear components i=φ i {u}=f i (u) u=φ u {i}=f u (i) Question: How can it be implemented? Answer: Semiconductive devices 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 5
Diode: Si crystal and doping The electrical characteristics of silicon and germanium are improved by adding materials in a process called doping. There are just two types of doped semiconductor materials: n-type materials contain an excess of conduction band electrons. (eg: Phosphor) p-type materials contain an excess of valence band holes.(eg.: Boron) 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 6
Diode: p-n junction One end of a silicon crystal can be doped as a p-type material and the other end as an n-type material. The result is a p-n junction. 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 7
Diode production: planar structure SiO 2 200μm Materials commonly used in the development of semiconductor devices: Silicon (Si) Germanium (Ge) Gallium Arsenide (GaAs) p n Next slides Metal bearing 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 8
Diode: p-n junction (cont ) The excess conduction-band electrons onthen-typesideareattractedtothe valence-band holes on the p-type side. The electrons in the n-type material migrate across the junction to the p- type material (electron flow). The electron migration results in a negative charge on the p-type side of the junction and a positive charge on the n-type side of the junction. The result is the formation of a depletion region around the junction. 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 9
Diode: p-n junction (cont ) External voltage is applied, a diode has three operating conditions: No bias: u D =0V i D =0A Reverse bias: external voltage across the p-n junction in the opposite polarity of the p- and n-type materials. u D <0V i D =0A Forward bias: external voltage across the p-n junction in the same polarity as the p- and n-type materials. u D >0V i D >0A 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 10
Actuel diode characterestics UT i =Φ i {} u = I e u 0 1 i 0 {} ln I 1 u = Φ u i = UT e + U T kt q B = I 0 is the reverse bias saturation current, U T is the thermal voltage. 26mV 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 11
Zener range (or breakdown range) The Zener region is in the diode s reverse-bias region. At some point the reverse bias voltage is so large the diode breaks down and the reverse current increases dramatically. The maximum reverse voltage that won t take a diode into the zener region is called the peak inverse voltage or peak reverse voltage. The voltage that causes a diode to enter the zener region of operation is called the zener voltage (u Z ). 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 12
Basic linear elements: Nonlinear resistive networks (circuits) Resistor, R, [Ω](Ohms) Nonlinear resistor (eg. diodes) Thevenin equivalent 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 13
Nonlinear resistive circuits (or networks) The system function: Nonlinear equation Question: How can it be solved? KVL and KVC: u + u + u = i R s D R 0 i = D 0 Charateristics of elements: u R = Ri R ud UT id = i0 e 1. ud UT us + Ri0 e 1 + ud = 0 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 14
Load-line analysis (graphical method) The load line plots all possible combinations of diode current (i D ) and voltage (u D ) for a given circuit. The maximum i D equals u s /R, and the maximum u D equals u s. The point where the load line and the characteristic curve intersect is the Q- point (equlibrium, or operation point set by the linear networks), which identifies i D and u D for a particular diode in a given circuit. 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 15
( ) Electrical measurements: Semiconductors basics: diodes and transistors x Newton-Raphson iterative method x f = n+ 1 n f ( xn ) ( x ) D f u = u + R I UT e 1 + u D s 0 D ud R I 0 UT D 1 UT ( ) f u = + e u n f ( x ) = 0 f(x) u ( n+ 1) ( n) D u = D ( ( n) ) D ( ( n) u ) D f u f x n xn+1 x 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 16
Some useful models of diode characteristics 1. Piecewise linear model: G = i D 0 u u = G( u u ) u u D 0 D 0 D 0 u 0 = 0 2. Series loss resistor model: i I0 u = Φ u {} i = UTln e + 1 + Rloss i 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 17
Semiconductors react differently to DC and AC currents. There are two types of resistance: DC (static) resistance AC (dynamic) resistance Resistance levels: static resistance For a specific applied DC voltage u D, the diode has a specific current i D, and a specific resistance R D. 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 18
Semiconductors react differently to DC and AC currents. There are two types of resistance: DC (static) resistance AC (dynamic) resistance: D In the forward bias region: r r D In the reverse bias region: r = D Resistance levels: dynamic resistance = du di D D D u, i Q Q 26mV = + R i loss 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 19
Types of diodes: Zener diode Zener diode Light-emitting diode Diode arrays Schottky diode Varactor diode Power diodes Tunnel diode Photodiode Photoconductive cells IR emitters Liquid crystal displays Solar cells Thermistors A Zener is a diode operated in reverse bias at the Zener voltage (u Z ). Common Zener voltages are between 1.8 V and 200 V. 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 20
Types of diodes: LED Zener diode Light-emitting diode Diode arrays Schottky diode Varactor diode Power diodes Tunnel diode Photodiode Photoconductive cells IR emitters Liquid crystal displays Solar cells Thermistors An LED emits photons when it is forward biased.these can be in the infrared or visible spectrum. The forward bias voltage is usually in the range of 2 V to 3 V. Applications: Instrumentation circuits as a sensor Alarmsystemsensor Detection of objects on a conveyor belt 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 21
Types of diodes: Schottky diode Zener diode Light-emitting diode Diode arrays Schottky diode Varactor diode Power diodes Tunnel diode Photodiode Photoconductive cells IR emitters Liquid crystal displays Solar cells Thermistors Characteristics: Lower forward voltage drop (0.2-.63V) Higher forward current (up to 75A) Significantly lower voltage drop Higher reverse current Faster switching rate Applications High frequency switching applications Low-voltage high-current applications AC-to-DC converters Communication equipment Instrumentation circuits 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 22
Types of diodes: Tunnel diode Zener diode Light-emitting diode Diode arrays Schottky diode Varactor diode Power diodes Tunnel diode Photodiode Photoconductive cells IR emitters Liquid crystal displays Solar cells Thermistors The characteristics of the tunnel diode indicate the negative resistance region. Note that this is only a small region of the characteristic curve. If the forward bias voltage is in the negative resistance region then the diode can be used as an oscillator. Applications: Oscillators Switching networks Pulse generators 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 23
Application of regular diodes: rectification The diode only conducts when it is forward biased, therefore only half of the AC cycle passes through the diode to the output. The DC output voltage is 0.318U p,whereu p is the peak AC voltage. 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 24
Application of simple diodes: rectification (cont ) Four diodes are connected in a bridge configuration. U DC = 0.636U p 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 25
There are two types of transistors: pnp npn The terminals are labeled: E - Emitter B-Base C - Collector Bipolar transistor construction 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 26
Bipolar transistor operation With the external sources, V EE (or U EE )andv CC (or U CC ), connected as shown: The emitter-base junction is forward biased The base-collector junction is reverse biased 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 27
Bipolar transistor configuration: common-base The base is common to both input (emitter base) and output (collector base) of the transistor. Operation mode B-E junction B-C junction Cutoff Close (V BE <0) Close(V CB >0) Normal active Open(V BE >0) Close Inverse active Close Open(V CB <0) Saturation Open Open I E = I C +I B I C = AI E I I C A = = A B 1 (Kirchhoff current law) (transitor equation) B 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 28
Bipolar transistor configuration: common-collector The input is on the base and the output is on the emitter. 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 29
Bipolar transistor configuration: common-emitter The emitter is common to both input (base-emitter) and output (collector-emitter). The input is on the base and the output is on the collector. 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 30
Common-emitter characteristics Base Characteristics Collector Characteristics 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 31
Bipolar transistor Modeling A model is an equivalent circuit that represents the AC characteristics of the transistor. A model uses circuit elements that approximate the behavior of the transistor. There are two models commonly used in small signal AC analysis of a transistor: r e model: the bipolar transistor is basically current-controlled device; therefore the r e model uses a diode and a current source to duplicate the behavior of the transistor. Hybrid equivalent model ( simplified equivalent model) 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 32
Simplified equivalent model: Ideal transistor = current controlled current sources i B U = r BE D i C = β i B 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 33
Similarities: Amplifiers Switching devices Field Effect Transistor (FET) Impedance matching circuits Differences: FETs are voltage controlled devices. Bipolar transistors are current controlled devices. FETs have a higher input impedance. Bipolar transistors have higher gains. FETs are less sensitive to temperature variations and are more easily integrated on ICs. FETs are generally more static sensitive than Bipolar transistors. 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 34
FET types JFET: Junction FET MOSFET: Metal Oxide Semiconductor FET D-MOSFET: Depletion MOSFET E-MOSFET: Enhancement MOSFET There are three terminals: Drain (D) and Source (S) are connected to the n-channel Gate (G) is connected to the p- type material 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 35
JFET operating characterictics There are three basic operating conditions for a JFET: V GS = 0, V DS increasing to some positive value Pinch Off V GS < 0, V DS at some positive value Voltage-controlled resistor: At the pinch-off point any further increase in U GS does not produce any increase in I D. V GS at pinch-off is denoted as V poff. I D is at saturation or maximum. It is referred to as I DSS. 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 36
JFET transfer characteristics In a JFET, the relationship of V GS (output) is a little more complicated: I (input) and I D D = I V DSS 1 V GS P 2 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 37
FET types JFET: Junction FET MOSFET: Metal Oxide Semiconductor FET D-MOSFET: Depletion MOSFET E-MOSFET: Enhancement MOSFET 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 38
MOSFET operating characterictics A depletion-type MOSFET can operate in two modes: Depletion mode: When V GS = 0 V, I D = I DSS When V GS < 0 V, I D < I DSS The formula used to plot the transfer curve still applies: I D = IDSS 1 V V GS Poff 2 Enhancement mode: These devices are off at zero gate source voltage U GS, and can be turned on by pulling the gate voltage in the direction of the drain voltage. 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 39
Summary Diodes are two-terminal devices that conduct current easily in one direction, but not in the other. The ideal diode model is a short circuit for forward currents and an open circuit for reverse voltages. Zener diodes are intended to operate in the breakdown region. Transistors are three-terminal devices. Circuits containing a nonlinear device can be analyzed using a graphical technique called a load-line analysis. The analysis of nonlinear electronic circuits is often accomplished in two steps: First, the dc operating point is determined, and a linear small-signal equivalent circuit is found; second, the equivalent circuit is analyzed. Next lecture: Nonlinear resistive networks 2011.10.05.. TÁMOP 4.1.2-08/2/A/KMR-2009-0006 40