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    The GAP/R K2-W Vacuum-Tube Op Amp in SPICE (Part 4): LTspice Files

    Dec. 9, 2024
    As a service to our readers, we're providing the LTspice files used in Dr. Dyer's article on simulation of the 12AX7 and the K2-W vacuum-tube op amp.
    Related To:

    As a service to our readers, we're sharing Stephen Dyer's LTspice files from his Electronic Design article "Modeling on Mondays: The GAP/R K2-W Vacuum-Tube Op Amp in SPICE (Part 4)."

    Stephen A. “Jack” Dyer
    1. The model for the K2-W is established as a hierarchical block in LTspice, with the schematic as shown. The two 62-V independent voltage sources represent the two neon lamps used in the actual circuit as voltage regulators. Positive feedback is applied to the second stage via resistor R7. Capacitor C1 is a Miller-effect capacitor.
    1. The model for the K2-W is established as a hierarchical block in LTspice, with the schematic as shown. The two 62-V independent voltage sources represent the two neon lamps used in the actual circuit as voltage regulators. Positive feedback is applied to the second stage via resistor R7. Capacitor C1 is a Miller-effect capacitor.
    Stephen A. “Jack” Dyer
    2. The LTspice schematic of the K2-W op amp in a basic inverting configuration incorporates the symbol created for the K2-W model. The gain G is set to ‒1. Two power supplies, +300 V and ‒300 V, are required for operation. The voltage source Vos_null compensates approximately for the K2-W’s inherent input-offset voltage; the details of the bias-adjustment circuitry aren’t shown.
    2. The LTspice schematic of the K2-W op amp in a basic inverting configuration incorporates the symbol created for the K2-W model. The gain G is set to ‒1. Two power supplies, +300 V and ‒300 V, are required for operation. The voltage source Vos_null compensates approximately for the K2-W’s inherent input-offset voltage; the details of the bias-adjustment circuitry aren’t shown.

    K2-W and 12AX7 LTspice files c.2024 Endeavor Business Media

    AndyT's Nonlinearities blog arrives the first and third Monday of every month. To make sure you don't miss the latest edition, new articles, or breaking news coverage, please subscribe to our Electronic Design Today newsletter.

    Bdieseldorff - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3936976
    K2-W op amp
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    Vacuum tubes
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    Learning about SPICE modeling