Improved vacuum tube models for SPICE simulations.docx

Improved vacuum tube models for SPICE simulations Part 1: Models and example by Norman L. Koren io/ SPICE ,anelectronic circuit simulation program originally developed at the University ofCalifornia atBerkeley, has found wide acceptance in the electronics and semiconductor industries. Itcan perform highly accurate time and frequency domain analysis plex analog and digital circuits (including harmonic and IMdistortion). mercial versions ofSPICE run puters, most notably PSpice from OrCAD .The downloadable PSspice student version (version atlast look) has limited capabilities bystandards ofsolid-state circuit design, but itcan beamazingly useful insimulating vacuum tube amplifiers, which tend tohave ponents. Itwas used for all examples inthis article. It's hard tofind onthe OrCAD website. Ihad togotothe CadencePCB home page and click onAll Downloads .Other well-known SPICE implementations include Electronics Workbench ,800-263-5552, and ICAP/4, from Intusoft , Box 710 San Pedro, CA90733-0710; 310-833-0710. Duncan Munro's list ofSPICE vendors may contain some hidden treasures. WinSpice isafree Spice3F4 Port for Windows 95, 98, 2000 &NT. Very intriguing. Itwill simulate much larger circuits than evaluation PSpice. SPICE contains built-in models for passive devices (resistors, capacitors, inductors, etc.) and for most active semiconductor devices (bipolar transistors, FETs, OpAmps, etc.), but none for vacuum tubes. SPICE models and can bedownloaded from manufacturer's Websites. Equations for vacuum tubes Scott Reynolds 1and Marshall Leach 2model vacuum tubes as voltage-controlled current sources whose output current isaweighted sum ofcontrolling element voltages raised tothe three-halves power. The controlling elements are different for triodes and pentodes. (Since the suppressor grid has little effect onthe transfer characteristics, pentodes are modeled astetrodes.) The plate current equation for triodes isI P=(E G+E P/ μ) 3/2/ k G1for E