The Transistor Amplifier
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Chapter 7: AC Transistor Amplifiers
Chapter 7: Transistors, part 2 Chapter 7: AC Transistor Amplifiers The transistor amplifiers that we studied in the last chapter have some serious problems for use in AC signals. Their most serious shortcoming is that there is a “dead region” where small signals do not turn on the transistor. So, if your signal is smaller than 0.6 V, or if it is negative, the transistor does not conduct and the amplifier does not work. Design goals for an AC amplifier Before moving on to making a better AC amplifier, let’s define some useful terms. We define the output range to be the range of possible output voltages. We refer to the maximum and minimum output voltages as the rail voltages and the output swing is the difference between the rail voltages. The input range is the range of input voltages that produce outputs which are not at either rail voltage. Our goal in designing an AC amplifier is to get an input range and output range which is symmetric around zero and ensure that there is not a dead region. To do this we need make sure that the transistor is in conduction for all of our input range. How does this work? We do it by adding an offset voltage to the input to make sure the voltage presented to the transistor’s base with no input signal, the resting or quiescent voltage , is well above ground. In lab 6, the function generator provided the offset, in this chapter we will show how to design an amplifier which provides its own offset. -
Power Electronics
Diodes and Transistors Semiconductors • Semiconductor devices are made of alternating layers of positively doped material (P) and negatively doped material (N). • Diodes are PN or NP, BJTs are PNP or NPN, IGBTs are PNPN. Other devices are more complex Diodes • A diode is a device which allows flow in one direction but not the other. • When conducting, the diodes create a voltage drop, kind of acting like a resistor • There are three main types of power diodes – Power Diode – Fast recovery diode – Schottky Diodes Power Diodes • Max properties: 1500V, 400A, 1kHz • Forward voltage drop of 0.7 V when on Diode circuit voltage measurements: (a) Forward biased. (b) Reverse biased. Fast Recovery Diodes • Max properties: similar to regular power diodes but recover time as low as 50ns • The following is a graph of a diode’s recovery time. trr is shorter for fast recovery diodes Schottky Diodes • Max properties: 400V, 400A • Very fast recovery time • Lower voltage drop when conducting than regular diodes • Ideal for high current low voltage applications Current vs Voltage Characteristics • All diodes have two main weaknesses – Leakage current when the diode is off. This is power loss – Voltage drop when the diode is conducting. This is directly converted to heat, i.e. power loss • Other problems to watch for: – Notice the reverse current in the recovery time graph. This can be limited through certain circuits. Ways Around Maximum Properties • To overcome maximum voltage, we can use the diodes in series. Here is a voltage sharing circuit • To overcome maximum current, we can use the diodes in parallel. -
Notes for Lab 1 (Bipolar (Junction) Transistor Lab)
ECE 327: Electronic Devices and Circuits Laboratory I Notes for Lab 1 (Bipolar (Junction) Transistor Lab) 1. Introduce bipolar junction transistors • “Transistor man” (from The Art of Electronics (2nd edition) by Horowitz and Hill) – Transistors are not “switches” – Base–emitter diode current sets collector–emitter resistance – Transistors are “dynamic resistors” (i.e., “transfer resistor”) – Act like closed switch in “saturation” mode – Act like open switch in “cutoff” mode – Act like current amplifier in “active” mode • Active-mode BJT model – Collector resistance is dynamically set so that collector current is β times base current – β is assumed to be very high (β ≈ 100–200 in this laboratory) – Under most conditions, base current is negligible, so collector and emitter current are equal – β ≈ hfe ≈ hFE – Good designs only depend on β being large – The active-mode model: ∗ Assumptions: · Must have vEC > 0.2 V (otherwise, in saturation) · Must have very low input impedance compared to βRE ∗ Consequences: · iB ≈ 0 · vE = vB ± 0.7 V · iC ≈ iE – Typically, use base and emitter voltages to find emitter current. Finish analysis by setting collector current equal to emitter current. • Symbols – Arrow represents base–emitter diode (i.e., emitter always has arrow) – npn transistor: Base–emitter diode is “not pointing in” – pnp transistor: Emitter–base diode “points in proudly” – See part pin-outs for easy wiring key • “Common” configurations: hold one terminal constant, vary a second, and use the third as output – common-collector ties collector -
ECE 255, MOSFET Basic Configurations
ECE 255, MOSFET Basic Configurations 8 March 2018 In this lecture, we will go back to Section 7.3, and the basic configurations of MOSFET amplifiers will be studied similar to that of BJT. Previously, it has been shown that with the transistor DC biased at the appropriate point (Q point or operating point), linear relations can be derived between the small voltage signal and current signal. We will continue this analysis with MOSFETs, starting with the common-source amplifier. 1 Common-Source (CS) Amplifier The common-source (CS) amplifier for MOSFET is the analogue of the common- emitter amplifier for BJT. Its popularity arises from its high gain, and that by cascading a number of them, larger amplification of the signal can be achieved. 1.1 Chararacteristic Parameters of the CS Amplifier Figure 1(a) shows the small-signal model for the common-source amplifier. Here, RD is considered part of the amplifier and is the resistance that one measures between the drain and the ground. The small-signal model can be replaced by its hybrid-π model as shown in Figure 1(b). Then the current induced in the output port is i = −gmvgs as indicated by the current source. Thus vo = −gmvgsRD (1.1) By inspection, one sees that Rin = 1; vi = vsig; vgs = vi (1.2) Thus the open-circuit voltage gain is vo Avo = = −gmRD (1.3) vi Printed on March 14, 2018 at 10 : 48: W.C. Chew and S.K. Gupta. 1 One can replace a linear circuit driven by a source by its Th´evenin equivalence. -
Basic DC Motor Circuits
Basic DC Motor Circuits Living with the Lab Gerald Recktenwald Portland State University [email protected] DC Motor Learning Objectives • Explain the role of a snubber diode • Describe how PWM controls DC motor speed • Implement a transistor circuit and Arduino program for PWM control of the DC motor • Use a potentiometer as input to a program that controls fan speed LWTL: DC Motor 2 What is a snubber diode and why should I care? Simplest DC Motor Circuit Connect the motor to a DC power supply Switch open Switch closed +5V +5V I LWTL: DC Motor 4 Current continues after switch is opened Opening the switch does not immediately stop current in the motor windings. +5V – Inductive behavior of the I motor causes current to + continue to flow when the switch is opened suddenly. Charge builds up on what was the negative terminal of the motor. LWTL: DC Motor 5 Reverse current Charge build-up can cause damage +5V Reverse current surge – through the voltage supply I + Arc across the switch and discharge to ground LWTL: DC Motor 6 Motor Model Simple model of a DC motor: ❖ Windings have inductance and resistance ❖ Inductor stores electrical energy in the windings ❖ We need to provide a way to safely dissipate electrical energy when the switch is opened +5V +5V I LWTL: DC Motor 7 Flyback diode or snubber diode Adding a diode in parallel with the motor provides a path for dissipation of stored energy when the switch is opened +5V – The flyback diode allows charge to dissipate + without arcing across the switch, or without flowing back to ground through the +5V voltage supply. -
6 Insulated-Gate Field-Effect Transistors
Chapter 6 INSULATED-GATE FIELD-EFFECT TRANSISTORS Contents 6.1 Introduction ......................................301 6.2 Depletion-type IGFETs ...............................302 6.3 Enhancement-type IGFETs – PENDING .....................311 6.4 Active-mode operation – PENDING .......................311 6.5 The common-source amplifier – PENDING ...................312 6.6 The common-drain amplifier – PENDING ....................312 6.7 The common-gate amplifier – PENDING ....................312 6.8 Biasing techniques – PENDING ..........................312 6.9 Transistor ratings and packages – PENDING .................312 6.10 IGFET quirks – PENDING .............................313 6.11 MESFETs – PENDING ................................313 6.12 IGBTs ..........................................313 *** INCOMPLETE *** 6.1 Introduction As was stated in the last chapter, there is more than one type of field-effect transistor. The junction field-effect transistor, or JFET, uses voltage applied across a reverse-biased PN junc- tion to control the width of that junction’s depletion region, which then controls the conduc- tivity of a semiconductor channel through which the controlled current moves. Another type of field-effect device – the insulated gate field-effect transistor, or IGFET – exploits a similar principle of a depletion region controlling conductivity through a semiconductor channel, but it differs primarily from the JFET in that there is no direct connection between the gate lead 301 302 CHAPTER 6. INSULATED-GATE FIELD-EFFECT TRANSISTORS and the semiconductor material itself. Rather, the gate lead is insulated from the transistor body by a thin barrier, hence the term insulated gate. This insulating barrier acts like the di- electric layer of a capacitor, and allows gate-to-source voltage to influence the depletion region electrostatically rather than by direct connection. In addition to a choice of N-channel versus P-channel design, IGFETs come in two major types: enhancement and depletion. -
Differential Amplifiers
www.getmyuni.com Operational Amplifiers: The operational amplifier is a direct-coupled high gain amplifier usable from 0 to over 1MH Z to which feedback is added to control its overall response characteristic i.e. gain and bandwidth. The op-amp exhibits the gain down to zero frequency. Such direct coupled (dc) amplifiers do not use blocking (coupling and by pass) capacitors since these would reduce the amplification to zero at zero frequency. Large by pass capacitors may be used but it is not possible to fabricate large capacitors on a IC chip. The capacitors fabricated are usually less than 20 pf. Transistor, diodes and resistors are also fabricated on the same chip. Differential Amplifiers: Differential amplifier is a basic building block of an op-amp. The function of a differential amplifier is to amplify the difference between two input signals. How the differential amplifier is developed? Let us consider two emitter-biased circuits as shown in fig. 1. Fig. 1 The two transistors Q1 and Q2 have identical characteristics. The resistances of the circuits are equal, i.e. RE1 = R E2, RC1 = R C2 and the magnitude of +VCC is equal to the magnitude of �VEE. These voltages are measured with respect to ground. To make a differential amplifier, the two circuits are connected as shown in fig. 1. The two +VCC and �VEE supply terminals are made common because they are same. The two emitters are also connected and the parallel combination of RE1 and RE2 is replaced by a resistance RE. The two input signals v1 & v2 are applied at the base of Q1 and at the base of Q2. -
Simple Blocking Oscillator Performance Analysis for Battery Voltage Enhancement
Journal of Mobile Multimedia, Vol. 11, No.3&4 (2015) 321-329 © Rinton Press SIMPLE BLOCKING OSCILLATOR PERFORMANCE ANALYSIS FOR BATTERY VOLTAGE ENHANCEMENT DEWANTO HARJUNOWIBOWO ESMART, Physics Education Department, Sebelas Maret University, Indonesia [email protected] RESTU WIDHI HASTUTI Physics Education Department, Sebelas Maret University, Indonesia [email protected] KENNY ANINDIA RATOPO Physics Education Department, Sebelas Maret University, Indonesia [email protected] ANIF JAMALUDDIN ESMART, Physics Education Department, Sebelas Maret University, Indonesia [email protected] SYUBHAN ANNUR FKIP MIPA, Lambung Mangkurat University, Indonesia An application Blocking Oscillator (BO) on a battery to power a system LED lamp light detector has been built and compared with a standard system used phone cellular adapter as the power supply. The performance analysis was carried out to determine the efficiency of the blocking oscillator and its potency to be adopted in an electronic appliance using low voltage and current from a battery. Measurements were taken using an oscilloscope, a multimeter, and a light meter. The results show that the system generates electrical pulses of 1.5 to 7.6 VDC and powering the system normally. The system generates 3.167 mW powers to produce the intensity of 176 Lux. On the contrary, the standard system needs 1.8mW to produce 5 Lux. A LED usually takes at least 60mW to get 7150 Lux. Therefore, the system used a simple blocking oscillator seems potential to provide high voltage for powering electronic appliances with low current. Key words: blocking oscillator, characteristic, efficiency, LED, pulse 1 Introduction A design of circuit based on blocking oscillator for light up a LED using waste battery was carried out. -
The Transistor, Fundamental Component of Integrated Circuits
D The transistor, fundamental component of integrated circuits he first transistor was made in (SiO2), which serves as an insulator. The transistor, a name derived from Tgermanium by John Bardeen and In 1958, Jack Kilby invented the inte- transfer and resistor, is a fundamen- Walter H. Brattain, in December 1947. grated circuit by manufacturing 5 com- tal component of microelectronic inte- The year after, along with William B. ponents on the same substrate. The grated circuits, and is set to remain Shockley at Bell Laboratories, they 1970s saw the advent of the first micro- so with the necessary changes at the developed the bipolar transistor and processor, produced by Intel and incor- nanoelectronics scale: also well-sui- the associated theory. During the porating 2,250 transistors, and the first ted to amplification, among other func- 1950s, transistors were made with sili- memory. The complexity of integrated tions, it performs one essential basic con (Si), which to this day remains the circuits has grown exponentially (dou- function which is to open or close a most widely-used semiconductor due bling every 2 to 3 years according to current as required, like a switching to the exceptional quality of the inter- “Moore's law”) as transistors continue device (Figure). Its basic working prin- face created by silicon and silicon oxide to become increasingly miniaturized. ciple therefore applies directly to pro- cessing binary code (0, the current is blocked, 1 it goes through) in logic cir- control gate cuits (inverters, gates, adders, and memory cells). The transistor, which is based on the switch source drain transport of electrons in a solid and not in a vacuum, as in the electron gate tubes of the old triodes, comprises three electrodes (anode, cathode and gate), two of which serve as an elec- transistor source drain tron reservoir: the source, which acts as the emitter filament of an electron gate insulator tube, the drain, which acts as the col- source lector plate, with the gate as “control- gate drain ler”. -
Fundamentals of MOSFET and IGBT Gate Driver Circuits
Application Report SLUA618A–March 2017–Revised October 2018 Fundamentals of MOSFET and IGBT Gate Driver Circuits Laszlo Balogh ABSTRACT The main purpose of this application report is to demonstrate a systematic approach to design high performance gate drive circuits for high speed switching applications. It is an informative collection of topics offering a “one-stop-shopping” to solve the most common design challenges. Therefore, it should be of interest to power electronics engineers at all levels of experience. The most popular circuit solutions and their performance are analyzed, including the effect of parasitic components, transient and extreme operating conditions. The discussion builds from simple to more complex problems starting with an overview of MOSFET technology and switching operation. Design procedure for ground referenced and high side gate drive circuits, AC coupled and transformer isolated solutions are described in great details. A special section deals with the gate drive requirements of the MOSFETs in synchronous rectifier applications. For more information, see the Overview for MOSFET and IGBT Gate Drivers product page. Several, step-by-step numerical design examples complement the application report. This document is also available in Chinese: MOSFET 和 IGBT 栅极驱动器电路的基本原理 Contents 1 Introduction ................................................................................................................... 2 2 MOSFET Technology ...................................................................................................... -
Power MOSFET Basics by Vrej Barkhordarian, International Rectifier, El Segundo, Ca
Power MOSFET Basics By Vrej Barkhordarian, International Rectifier, El Segundo, Ca. Breakdown Voltage......................................... 5 On-resistance.................................................. 6 Transconductance............................................ 6 Threshold Voltage........................................... 7 Diode Forward Voltage.................................. 7 Power Dissipation........................................... 7 Dynamic Characteristics................................ 8 Gate Charge.................................................... 10 dV/dt Capability............................................... 11 www.irf.com Power MOSFET Basics Vrej Barkhordarian, International Rectifier, El Segundo, Ca. Discrete power MOSFETs Source Field Gate Gate Drain employ semiconductor Contact Oxide Oxide Metallization Contact processing techniques that are similar to those of today's VLSI circuits, although the device geometry, voltage and current n* Drain levels are significantly different n* Source t from the design used in VLSI ox devices. The metal oxide semiconductor field effect p-Substrate transistor (MOSFET) is based on the original field-effect Channel l transistor introduced in the 70s. Figure 1 shows the device schematic, transfer (a) characteristics and device symbol for a MOSFET. The ID invention of the power MOSFET was partly driven by the limitations of bipolar power junction transistors (BJTs) which, until recently, was the device of choice in power electronics applications. 0 0 V V Although it is not possible to T GS define absolutely the operating (b) boundaries of a power device, we will loosely refer to the I power device as any device D that can switch at least 1A. D The bipolar power transistor is a current controlled device. A SB (Channel or Substrate) large base drive current as G high as one-fifth of the collector current is required to S keep the device in the ON (c) state. Figure 1. Power MOSFET (a) Schematic, (b) Transfer Characteristics, (c) Also, higher reverse base drive Device Symbol. -
CLASS 331 OSCILLATORS January 2011
CLASS 331 OSCILLATORS 331 - 1 331 OSCILLATORS 94.1 MOLECULAR OR PARTICLE RESONANT 34 .Particular frequency control TYPE (E.G., MASER) means 1 R AUTOMATIC FREQUENCY STABILIZATION 35 ..Electromechanical (e.g., motor) USING A PHASE OR FREQUENCY 36 R ..Reactance device (e.g., SENSING MEANS variable capacitors, saturable 2 .Plural oscillators controlled inductors, reactance tubes, 3 .Molecular resonance etc.) stabilization 36 C ...Capacitor controlled AFC 4 .Search sweep of oscillator 36 L ...Inductor controlled AFC 5 .Magnetron oscillator 1 A .AFC with logic elements 6 .Klystron oscillator 37 BEAT FREQUENCY 7 ..Plural controls 38 .Plural beating 8 .Transistorized controls 39 ..Single channel 9 .Oscillator with distributed 40 .Frequency or amplitude parameter-type discriminator adjustment or control 10 .Plural A.F.S. for a single 41 .Frequency stabilization oscillator 42 .With particular signal combining 11 ..Plural comparators or means (e.g., cavity mixer) discriminators 43 ..With filter in mixer output 12 ...With phase-shifted inputs circuit 13 ..Motor control of oscillator 44 WITH FREQUENCY CALIBRATION OR 14 .With intermittent comparison TESTING controls 45 POLYPHASE OUTPUT 15 .Amplitude compensation 46 PLURAL OSCILLATORS 16 .Tuning compensation 47 .Oscillator used to vary 17 .Particular error voltage control amplitude or frequency of (e.g., intergrating network) another oscillator 18 .With reference oscillator or 48 .Adjustable frequency source 49 .Selectively connected to common 19 ..Spectrum reference source output or oscillator substitution