Working Principle and Application of Shaded-Shaped Inverter Circuit

1. Principle

The principle of the screen-shaft split inverter circuit is shown in the figure above.

The unilaterally amplified audio signal is input from the IN terminal and added to the gate of the electron tube Vl. In the screen and cathode circuits of Vl, two load resistors R2 and R3 with equal resistance are respectively connected. After the audio signal is amplified by VI, two voltages of equal magnitude and opposite phases are output from the screen and cathode (from the Tl and T2 terminals) respectively, which drive the power amplifier electron tube to work.

2. Application examples

As shown in the figure below, the unilateral audio signal voltage is input from the IN terminal to the left triode grid (1) pin of the electron tube V1 (6H8C), and after amplification, the audio voltage is output at the screen (2) pin. This voltage is directly added to the right triode grid (4) pin. After amplification by the right triode, two equal and opposite excitation voltages are output at its screen (5) pin and cathode (6) pin respectively, driving the two power tubes of the power amplifier stage to work.

Among them, the left transistor screen (2) pin is connected to the right transistor grid (4) pin, the voltage of the right transistor grid (4) pin is +66V, the voltage on the cathode (6) pin is +70V, the grid (4) pin voltage is 4V lower than the cathode (6) pin voltage, that is, the grid bias voltage of the right transistor is -4V. Direct cross-coupling of the two tubes can reduce distortion. R5 and C3 are frequency compensation circuits.