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AN-802 Crystal-Measuring Oscillator Negative Resistance

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Crystal - Measuring Oscillator Negative AN-802 Resistance APPLICATION NOTE Introduction Negative resistance models the required gain needed from the active network to sustain stable oscillations. The negative resistance model is shown in Figure 1. The crystal is represented by a reactance term Xm and a motional resistance term Rm. The active network is represented by the reactance term Xosc and the Resistance term -Rneg where Rneg is the negative resistance of the inverter amplifier. One process used as a means to easily evaluate the negative resistance characteristics and oscillation allowance of an oscillator circuits is the method of adding a resistor to the hot terminal of the crystal unit and observing whether it can oscillate (examining the negative resistance). The oscillator circuit capacity can be examined by changing the value of the added resistance. Figure 1. Negative Resistance Model Measuring Negative Resistance of the Active Network The steps for measuring the negative resistance of the active network are as follows: 1) Compute crystal parameters Co, Cs, Ls, Rs and CL using a Network Analyzer such as 250B/C by Saunders and Associated Inc. 2) Solder crystal on X1 and X2 pins of the IDT clock IC and mount the crystal load capacitors next to the device pins (as shown in Figure 2). 3) Adjust the load capacitance to get the output frequency error to nearly 0ppm (account for contribution due to stray capacitance on the PCB board). 4) Connect a series resistor Rx (as shown in Figure 2) and keep increasing its value until oscillations stop occurring on powering up the device. 5) The negative resistance of the active network is then equal to Rx + Rs. AN-802 REVISION B 03/12/14 1 ©2014 Integrated Device Technology, Inc. AN-802 CRYSTAL - MEASURING OSCILLATOR NEGATIVE RESISTANCE Figure 2. Active Network AN-802 REVISION B 03/12/14 2 AN-802 CRYSTAL - MEASURING OSCILLATOR NEGATIVE RESISTANCE Corporate Headquarters Sales Tech Support 6024 Silver Creek Valley Road 1-800-345-7015 or email: [email protected] San Jose, CA 95138 USA 408-284-8200 480-763-2056 Fax: 408-284-2775 www.IDT.com DISCLAIMER Integrated Device Technology, Inc. (IDT) and its subsidiaries reserve the right to modify the products and/or specifications described herein at any time and at IDT’s sole discretion. All information in this document, including descriptions of product features and performance, is subject to change without notice. Performance specifications and the operating parameters of the described products are determined in the independent state and are not guaranteed to perform the same way when installed in customer products. The information contained herein is provided without representation or warranty of any kind, whether express or implied, including, but not limited to, the suitability of IDT’s products for any particular purpose, an implied warranty of merchantability, or non-infringement of the intellectual property rights of others. This document is presented only as a guide and does not convey any license under intellectual property rights of IDT or any third parties. IDT’s products are not intended for use in applications involving extreme environmental conditions or in life support systems or similar devices where the failure or malfunction of an IDT product can be reasonably expected to signifi- cantly affect the health or safety of users. Anyone using an IDT product in such a manner does so at their own risk, absent an express, written agreement by IDT. Integrated Device Technology, IDT and the IDT logo are registered trademarks of IDT. Product specification subject to change without notice. Other trademarks and service marks used herein, including protected names, logos and designs, are the property of IDT or their respective third party owners. Copyright 2014. 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    Silicon Controlled Rectifier Silicon Controlled Rectifier (SCR) is a very important member of the family of four layer pnpn devices. Some of the other members of the family are Shockley Diodes, Silicon Controlled Switch, Triac, Diac, etc. All these devices are capable of handling large currents, and hence they are rapidly taking the status of essential components in industrial applications. The application areas of SCR include relay controls, regulated power supplies, motor controls, invertors, battery chargers, protection circuits, heater controls, etc. The SCR is a three terminal, three junction device. The three terminals are called Anode, Cathode and Gate as shown in Fig. 1. The figure also shows the three junctions and circuit symbol of the device. The operation of SCR can be understood by splitting the four layer pnpn structure into two three layer transistor structures as shown in figure 2 (a) and then analyzing the resultant of Fig. 2 (b). Figure 1 Note that one transistor is pnp while the other is npn. These two transistors form a feedback circuit. Let us first consider the case where the gate is at zero potential with respect to the cathode and a positive potential is applied to the anode. VBE2 = Base emitter voltage of transistor Q2 = VAK = 0. Figure 2 So IB2 = 0 and I C2 ≅ I CO The base current of transistor Q1 is IB1 = IC2 ≅ I CO which is too strong to turn Q1 ON. Both transistors are therefore in the OFF state and the anode current IA = I CO. This represints the OFF state of the SCR.
  • Power Transfer Analysis of an Asymmetric Wireless Transmission System Using the Scattering Parameters

    Power Transfer Analysis of an Asymmetric Wireless Transmission System Using the Scattering Parameters

    electronics Article Power Transfer Analysis of an Asymmetric Wireless Transmission System Using the Scattering Parameters Živadin Despotovi´c , Dejan Relji´c* , Veran Vasi´c and Djura Oros Department of Power, Electronic and Telecommunication Engineering, Faculty of Technical Sciences, University of Novi Sad, Novi Sad 21000, Serbia; [email protected] (Ž.D.); [email protected] (V.V.); [email protected] (D.O.) * Correspondence: [email protected]; Tel.: +381-21-485-4545 Abstract: The most widely adopted category of the mid-range wireless power transmission (WPT) systems is based on the magnetic resonance coupling (MRC), which is appropriate for a very wide range of applications. The primary concerns of the WPT/MRC system design are the power transfer capabilities. Using the scattering parameters based on power waves, the power transfer of an asymmetric WPT/MRC system with the series-series compensation structure is studied in this paper. This approach is very convenient since the scattering parameters can provide all the relevant characteristics of the WPT/MRC system related to power propagation. To maintain the power transfer capability of the WPT/MRC system at a high level, the scattering parameter S21 is used to determine the operating frequency of the power source. Nevertheless, this condition does not coincide with the maximum possible power transfer efficiency of the system. In this regard, the WPT/MRC system is thereafter configured with a matching circuit, whereas the scattering parameter 0 S21 S21’is used to calculate and then adjust the matching frequency of the system. This results in the maximum available power transfer efficiency and thereby increases the overall performance Citation: Despotovi´c,Ž.; Relji´c,D.; of the system.
  • SOME RECENT DEVELOPMENTS of REGENERATIVE Fication Which Is Based Fundamentally on Regeneration, but Which Existing Therein) Is E

    SOME RECENT DEVELOPMENTS of REGENERATIVE Fication Which Is Based Fundamentally on Regeneration, but Which Existing Therein) Is E

    SOME RECENT DEVELOPMENTS OF REGENERATIVE CIRCUITS* BY EDWIN H. ARMSTRONG (MARCELLUS HARTLEY RESEARCH LABORATORY, COLUMBIA UNIVERSITY, NEW YORK) It is the purpose of this paper to describe a method of ampli- fication which is based fundamentally on regeneration, but which involves the application of a principle and the attainment of a result which it is believed is new. This new result is obtained by the extension of regeneration into a field which lies beyond that hitherto considered its theoretical limit, and the process of amplification is therefore termed super-regeneration. Before proceeding with a description of this method it is in order to consider a few fundamental facts about regenerative circuits. It is well known that the effect of regeneration (that is, the supplying of energy to a circuit to reinforce the oscillations existing therein) is equivalent to introducing a negative resistance reaction in the circuit, which neutralizes positive resistance reaction, and thereby reduces the effective resistance of the cir- cuit. There are three conceivable relations between the nega- tive and positive resistances: namely-the negative resistance introduced may be less than the positive resistance, it may be equal to the positive resistance, or it may be greater than the positive resistance of the circuit. We will consider what occurs in a regenerative circuit con- taining inductance and capacity when an alternating electro- motive force of the resonant frequency is suddenly impressed for each of the three cases. In the first case (when the negative resistance is less than the positive), the free and forced oscillations have a maximum amplitude equal to the impnressed electomotive force over the effective resistance, and the free oscillation has a damping determined by this effective resistance.