High Precision Model of Small Triode Tube Considering Grid-Bias Positive/Negative Transition State

Abstract

We propose a unified high precision SPICE model miniature triode tube series. The model formula was devised by high precision measurement data of 12AX7, 12AU7, 12AY7, 12AT7. In the conventional model, the perveance value and the amplification factor, which are the basic parameters expressing the I-V characteristic, have been given respectively as a constant for each vacuum tube. We have found that these values are the modulation coefficient by operation conditions depending on the electrode shape. We proposed a new physical model incorporating the physical phenomena of space charge modulation including the threshold vicinity and positive grid bias. As a result, we succeeded for the first time to express the modulation of amplification factor with small signal characteristics parameters which enables to simulate the complicated non-linear behavior such as distortion property of amplifier.