| 摘要 |
PURPOSE:To improve effectively efficiency while keeping the calss A operation, by changing the bias according to the signal level independently of the frequency. CONSTITUTION:One input signal is supplied to a load through the push-pull amplifier circuit of transistors Tr9, 10, and the other is subjected to full-wave rectification in 2, and the output has the peak held by buffer amplifier 4 and capacitor 16. In case of a large instantaneous value of the input signal, diodes D17 and Tr18 are biased reversely to become a cutoff state, and Tr22 is cut off also, and the DC signal level at output terminal 5 of amplifier 4 is not discharged but is held in a level corresponding to the maximum value. When the input signal level becomes a prescribed value or less, D17 and Tr17, 33 are conductive, and the DC potential of terminal 5 is discharged with a high time constant, and this signal gives a bias voltage to the bases of Tr9, 10 through differential amplifier 6. Outputs of Tr10, 11 are fed back negatively to the inversion input of amplifier 6 through differential amplifier 14, thereby changing the bias values equal to Tr10, 11 according to the input level. |
