| 摘要 |
PURPOSE:To prevent occurrence of the distortion during the large input with a simple constitution, by securing the functions of the two transistors as a B-class push-pull amplifier each during the large input and at the same time varying the extent or the negative feedback. CONSTITUTION:In case the input level is high, AGC voltage E3 is small. And accordingly, DC voltage E5 applied to transistor (TR)Q5 is also reduced. Thus TRQ1, Q2 receive the B-class bias, and at the same time the working pont of TRQ3 reaches the saturation region to secure the function as an impedance element for TRQ3. And TRQ1, Q2 are turned into the B-class push-pull amplifiers with the current negative feedback applied. In this case, voltage E3 varies contrarily with change of the input level. Then the higher the input level the less collector current IS, and accordingly the collector current of TRQ13 is reduced to decrease the collector voltage. As a result, the impedance of TRQ3 is increased, and then the extent of the current negative feedback is increased to TRQ1, Q2 to decrease the gain. Thus the distortion occurring during the large input can be prevented. |
