A.V. Baranov1, A.L. Kozikov2

1,2 JSC SPE «SALUT» (Nizhny Novgorod, Russia)

1 baranov.micros@yandex.ru; 2 lehakozikov@yandex.ru

Introduction. There are known J-class power amplifiers, which, although are not switching devices, are quite correspond to high-efficiency devices. The transistor current in J-class amplifiers is described by cosine pulses with certain cut-off angles, and the voltage across it is selected so that the amplifier load has inductive reactance in order to compensate the transistor output capacitance at the fundamental frequency. Unfortunately, the choice of voltage form is not unambiguously defined for such a load.

Aim. In the process of creating load with inductive reactance, uncertainty should be eliminated when choosing the voltage form by proposing a modification of a J-class power amplifier, in which the output capacitance of its transistor is directly taken into account.

Materials and methods. Based on the proposed model of a J-class power amplifier, waveforms of current and voltage are obtained, in which the influence of the transistor output capacitance is considered by means of dimensionless parameter.

Results. The electronic efficiency of a J-class power amplifier and the normalized impedances of its loads at the fundamental frequency and its harmonics are calculated. For the received loads, a formula has been established for recalculating their normalized and non-normalized values. Using the calculated data, the input and output circuits of the J-class power amplifier are designed. Based on the results of machine modeling of these circuits, a device prototype has been made. It operates at a frequency of 915 MHz and has a supply voltage of +10 V. The dependences of its drain efficiency, output power, and consumption current on input power have been experimentally obtained. So, with a drain efficiency of ≈71% and a current of ~1A, the device prototype provides an output power of ~7 Watts with a compression of its amplitude characteristic of ~0.6 dB, and with a lower output power of ~6 Watts, it is a linear device.

Conclusion. A modification of a J-class power amplifier is proposed, in which the transistor output capacity is directly taken into account. The possibility of developing such amplifiers with relatively linear and broadband characteristics and with drain efficiency approaching the theoretical limit of 78.5%, which typical for class B and AB amplifiers, has been confirmed.

Baranov A.V., Kozikov A.L. Modification of the J-class power amplifier. Radiotekhnika. 2026. V. 90. № 2. P. 171−179. DOI: https://doi.org/10.18127/j00338486-202602-17 (In Russian)

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