Circuits Provide Nonlinearity  EDNDesign Ideas 02/28/2000 In analog design, you might need to create an amplifier with nonlinear dynamic characteristics—for example, logarithmic, exponential, or squarelaw. Usually, such amplifiers are complicated. However, the project often does not require mathematical precision. For example, you might just need to increase the dynamic range of an amplifier, or to eliminate saturation for an extended inputvoltage range. __ Circuit Design by Abel Raynus Circular slide rule provides quick results  EDNDesign Ideas  March 26, 1998 [ NOTE
: File has multiple design, scroll for this one.] In analogcircuit design, most calculations you make need not be very precise. If you need an LEDcurrent calculation or a couplingcapacitor value, for example, ±5% or even ±10% accuracy is usually adequate. It's sometimes inconvenient to make these calculations with a pocket calculator. For example, finding the cutoff frequency of a 3.3kiloohms/47pF network requires approximately 20 key presses. __ Circuit Design by Jacek Pawlowski, PW INMEL, Zielona Góra, Poland
Commutating Amp Performs Log Function  02/16/95 EDNDesign Ideas  Customarily, logarithmic amplifiers exploit the V/I characteristic of a pn junction or approximate a log function in a piecewiselinear fashion. Both approaches suffer from inherent limitations. A pn junction's V/I characteristic has large temperature coefficients requiring ad hoc compensation circuitry. Piecewiselinear approximations exhibit discontinuities in their first derivatives __ Circuit Design by Moshe Gerstenhaber and Stefano D'Aquino, Analog Devices, Wilmington, MA
Cubic Interpolation Hikes Table's Accuracy  02/16/95 EDNDesign Ideas  You can obtain very accurate approximations of a function from only a few data points contained in a lookup table, trading storage space for calculation time. For example, you can derive . __ Circuit Design by Brad Eckert, Industrial Commercial Electronics, Buffalo, NY
DSP Algorithm Measures Frequency & Damping  10/08/98 EDNDesign Ideas  The timedomain DSP algorithm described here allows you to measure the key parameters—natural frequency and damping—in linear, secondorder electromechanical systems. The method applies to a range of electromechanical transducers (electromagnetic or electrostatic], including dynamic speakers, seismic geophones, micromachined sensors, and other systemsContains several designs, scroll to find this one. __ Circuit Design by Olga Belousova, Los Alamos, NM, and Alexander Belousov, New York, NY
Efficient Algorithm Generates Random Signal  12/05/96 EDNDesign Ideas  A common way to simulate a sequence of bandwidthlimitednoise samples is to start with a sequence of uncorrelated random numbers that have a suitable distribution and then pass that sequence through a filter. Unfortunately, filtering affects the signal level, and the complexity of the filter makes computations inefficient. Alternatively, the VHDL algorithm in Listing 1 requires very little computation, __ Circuit Design by Ove Johansson, CelsiusTech Systems, Stockholm, Sweden
Fast algorithm computes histograms  10/28/99 EDNDesign Ideas  A histogram is a convenient method of presenting statistical features of data; you can use a histogram for an estimate of the probability density function of a random phenomenon. To prepare a histogram entails dividing the interval occupied by data values __ Circuit Design by Lukasz Sliwczynski
Genetic algorithms: programs that boggle the mind  EDN Design Ideas  03/03/1997 Assume that you construct a simple device consisting of a power source and two potentiometers in series with an incandescentlight bulb (Figure 1) . Assume also that you can rotate the potentiometers 180°, from 90° to +90°, and that the point of least resistance for each potentiometer is in its center (upright) position. Suppose you set the potentiometers to random positions, then you proffer the device to friends and ask them to play with itusing the potentiometers, not the supply voltageto make the light as bright as possible. Most people select one potentiometer, turn it a little to the left or right, and note the result. __ Circuit Design by Clive "Max" Maxfield, Intergraph Computer Systems
Hardware Random Number Generator  This page describes my effort to construct a random number generator with as high a securitytocost ratio as I can manage. I warn anyone who intends to use any of this for anything serious to engage in a rigorous study of the weaknesses inherent in this design. The PN junction of Q1 is reverse biased to produce avalanche noise __ Designed by Aaron Logue
Linear potentiometer provides nonlinear light intensity control  04/28/05 EDNDesign Ideas  Circuit matches light control to eye’s intensityresponse curve __ Circuit Design by Stephan Goldstein, Analog Devices, Wilmington, MA
Log Amp uses capacitorcharging law  01/10/02 EDNDesign Ideas  The novel logarithmic amplifier in Figure 1 relies on the exponential charging characteristics of a simple RC circuit. The expression for the time, T, required for a capacitor, C, to reach a voltage (VIN–VK) from 0V, when charged through a resistor, R, with an applied voltage of VIN, is VIN–VK=VIN (1–e–T/RC) , where VK is a fixed voltage. The expression for T reduces to T=RCln (VIN/VK) , clearly showing an inherent logarithmic characteristic. __ Circuit Design by Jayashree Raghuraman and Ajoy Raman, Aeronautical Development Establishment, Bangalore, India
Logratio Amplifier has sixdecade dynamic range  27Nov03 EDNDesign Ideas  You need opticalpower monitoring to guarantee overall system performance in fiberoptic communication systems. Logarithmicsignal processing can maintain precise measurements over a wide dynamic range. The widedynamicrange signal undergoes compression, and the use of a lower resolution measurement system then saves cost __ Circuit Design by Reza Moghimi, Analog Devices, San Jose, CA
Mathcad Functions Perform Log Interpolation  30Oct03 EDNDesign Ideas  MathCAD provIdeas a number of interpolation and curvefitting functions, so that, given a set of XY data points, you can estimate the Y value for any given X coordinate. Unfortunately, these functions work poorly with data that is to be displayed in a nonlinear (logarithmic] manner. Examples of these functions are Using the builtin "linterp" function, MathCAD estimates and plots the data (Fig __ Circuit Design by James Bach, Delphi Delco Electronics Systems, Kokomo, IN
Mixed Signal Algorithm Tests Transducers  04/24/97 EDNDesign Ideas  A simple test procedure (Reference 1) allows you to measure damping coefficient beta in electromechanical transducers, such as speakers, microphones, and seismic geophones. The method is based on stimulating the transducer with a dc step current, IS, and then separately integrating the positive and negative halfwaves of the transducer's terminal voltage, V (t) , after removing the step current. The integrals of the positive and negative waveforms contain all the necessary information to calculate beta. __ Circuit Design by Alex Belousov, Rego Park, NY
Model fixedpoint DSP arithmetic in C  03/18/99 EDNDesign Ideas  NOTE
: Page includes
several designs. Scroll to find this one. You can run initial highlevel simulations of custom numerical algorithms, such as digital filters, using floatingpoint numbers in an environment such as C or Matlab. Unfortunately, you won't see include fixedpoint effects, such as truncation due to limited precision and register overflow, until you use a Hardware Design Language (HDL) , such as Verilog or VHDL. However, a technique that models these effects in C—the function "bit_limit" in Listing 1—provIdeas faster execution and better portability than HDLs and allows early exploration of the tradeoff between bus width and performance. __ Circuit Design by Roger Maher, SSL Ltd, Dublin, Ireland
MotorDrive Algorithm Saves Space & Cycle  02/17/94 EDNDesign Ideas  The algorithm embodied in the second subroutine in Listing 1 generates the excitation sequence for most permanentmagnet and hybrid stepper motors. This subroutine is smaller than subroutines that spring from other algorithms __ Circuit Design by Jose A P Machado da Silva, University of Porto, Porto, Portugal
Nodal Analysis  (spice design) __ Designed by Rick
NonLinear DC Analysis  (spice design) __ Designed by Rick
Primer on binary arithmetic rounding  01/21/99 EDNDesign Ideas  NOTE
: Page includes
several designs. Scroll to find this one. As digital communications and data compression/decompression proliferate, signalprocessing functions grow in importance. Whether you’re dealing with hardwired logic or programmable engines, an understanding of binaryarithmetic rounding is important in getting correct and consistent results. Before we discuss rounding, consider a binary number (Figure 1) Page includes
several designs. Scroll to find this one __ Circuit Design by Tom Balph, Motorola SPS, Tempe, AZ
Provides More Accurate Multiplication  12/15/11 EDNDesign Ideas  Convert into and out of the sampleddata domain to get an accurate multiplication. Common analog multiplying devices employ methods using transistor parameters. Precise versions of these devices use the logarithm method of multiplication. This method involves the addition of logarithms and an exponential conversion (Reference 1) . Using these methods, you can achieve a minimal error of ±0.1%. This Design Idea reduces the error, employs readily available standard components, and maintains the correct voltage scale. __ Circuit Design by Yakov Velikson, Lexington, MA
Reference stabilizes exponential current  10/25/01 EDNDesign Ideas  In an antilog converter, the difference between the base voltages of two transistors sets the ratio of their collector currents The use of matched transistors balances the firstorder temperature coefficient but leaves a temperaturedependent gain term, q/kT. Classic antilog circuits use a thermistor in the drive circuitry to correct this temperature dependency __ Circuit Design by Tom Napier, North Wales, PA
Resistance Calculator Yields Precise Values  08/03/95 EDNDesign Ideas  For times when the nearest preferred resistor value isn't close enough to the desired value, a program comes in handy. (You'll find the executable ZIPfile and several sourcecode files for the program in EDN BBS /DI_SIG #1740.) The program finds all combinations of two series or parallel connected resistors, within a specified tolerance of the required value, using only preferred values from the E6, E12, E24, and E96 ranges (6, 12, 24, and 96 different values per decade) . __ Circuit Design by David Kirkby, Department of Medical Physics, University College London, London, UK/
Simple Circuits Provide Nonlinearity  EDNDesign Ideas 02/28/2000 In analog design, you might need to create an amplifier with nonlinear dynamic characteristics—for example, logarithmic, exponential, or squarelaw. Usually, such amplifiers are complicated. However, the project often does not require mathematical precision. For example, you might just need to increase the dynamic range of an amplifier, or to eliminate saturation for an extended inputvoltage range. __ Circuit Design by Abel Raynus
Single Ended Adder/Subtractor  This circuit shows Using Vcom as third algebraic input in an addition/subtraction circuit. This is useful for adding or translating signals. __ Linear Technology/Analog Devices App Note, Jul 2, 2012
Singlecycle logarithms & antilogs  11/11/13 EDNDesign Ideas  Here are some very fast log (and antilog) blocks wellsuited to FPGA implementation __ Circuit Design by Michael Dunn
Take a look inside the SPICE engine. How it works.  (spice design) __ Designed by Rick
Transient Analysis  One of the most complex and intriguing capabilities of the SPICE algorithm is the Transient Analysis. How do we take a collection of resistive and energystorage components, then find its time response to an arbitrary input waveform? Yes, you could formulate and solve the differential equations to get the response versus time, but SPICE is not a differential equation solver (spice design)
Use Derivatives to catch RF calibration errors  05/27/99 EDNDesign Ideas  Many RFsystem calibrations involve checking for minimum power available or removing system offsets. One example is the checking of an RF source’s output powerPDF has several circuits, please scroll to find this one. __ Circuit Design by Steven C Hageman, HewlettPackard Co, Santa Rosa, CA
Versatile powersupply load uses light bulbs  02/07/02 EDNDesign Ideas  Improvising loads for benchtesting and designing power supplies is often a frustrating and sometimes hazardous experience. When you push large power resistors to their limit, they tend to burn benches and melt solder connections. Many electronic loads are on the market but are usually expensive and of laboratorytype precision and often represent overkill for the average designer __ Circuit Design by William Sloot, Computron Display Systems, Mount Prospect, IL
White LED driver provides 64 step logarithmic dimming  10Jun04 EDNDesign Ideas  The circuit of Figure 1 is designed for portablepower applications that require white LEDs with adjustable, logarithmic dimming levels. The circuit drives as many as four white LEDs from a 3.3V source and adjusts the total LED current from 1 to 106 mA in 64 steps of 1 dB each. The driver is a charge pump that mirrors the current ISET (sourced from IC3's SET terminal] to produce a current o __ Circuit Design by William Hadden, Maxim Integrated Products, Sunnyvale, CA
