Dynamic feedback amplifier
for the basic principle: When the speaker supported the adoption of little change voltage
feedback when the speaker load at the same time for a change in the use of current feedback and voltage
feedback. The author of the dynamic feedback amplifier
circuit as shown below, from 4 to enlarge circuit. Input stage from Q1 ~ Q3 composition with emitter current source of differential amplifiers from the D2 ~ D4 is a wizard-voltage reference voltage
to Q3, and D2 ~ D4 and the equalizer
from Q4 and external components of the Constant current sources, increase the input level of stability and has a high common mode in capacity, changes in voltage
power grid, power grid disturbance, potential drift, drift, and so have more effect. Larger-voltage current source load for the amplifier, the constant current Yuanyou Q6, Q8 and its peripheral components composition, and Q6, Q8 and the equalizer
from another current source (from Q4 and its peripheral components constitute a) to provide And therefore has good and sufficient linear gain. The frequency of use of high-level, small junction capacitance in the power of the B649, the work of Group A in a single state, with the traditional way different. The third grade class-driven, bias voltage
from the Q7 and its peripheral circuit to provide the constant pressure circuit. Last Stage two pairs of high-power components of the current amplifier, their quiescent current is constant pressure from the circuit provided by the bias and bias resistor R24 ~ R27 common decision. R24 ~ R27 set up so that the upper stage will always be in micro-state status, and the environment from the impact of temperature. The circuit of the feedback from the network R8, C3, R9, R20 ~ R22 components such as dynamic feedback network. On the one hand by the C3, R9, R20, R21 DC servo passive components to complete the network output signal negative feedback, thereby not only to enlarge the role of DC and removed from its own source of interference with the active DC servo circuit, this set of For the mid-point, simple and effective way; On the other hand, dynamic feedback from the entire network together, so that the output level at the end of the signal to the speaker on the voltage
and current drive to minimize the distortion.
Installation, the output power can be Q13 ~ Q16, to promote the Q9, Q10 and the bias of the Q7 and Q5, Q6 mounted on a radiator, to ensure the stability of temperature. If we can not do this, all should be in the power of installing the appropriate size of the radiators to ensure the safety of the tubes.
Debugging, should be W1, W2 sliding contact transferred to the bottom of the map, W3 transferred to the top. Then boot electricity and W3 slow adjustment to the Q7 ce voltage
3.5 V guitar around. Then, W1 adjust to the point A potential to within ± 30mV. Boil for half an hour after the digital
multimeter measuring the output level Q15 and Q16 is among the two e-voltage, slow to adjust W3 for about 80 mV, at this time quiescent current output level of about 200 mA.
circuit only reference to the dynamics of this feedback can be converted into a dynamic network feedback amplifier.