Current of base is defined by Rb. At increase in current of a collector tension in a point And falls and therefore base current decreases, and it does not allow to increase further to collector current. But that base current, tension in a point began to change And has to change for 10-20%, that is Rk has to be very great that comes true only in low-power cascades. But that we will apply cross feedback, this scheme does not suit us.
In this academic year project the amplifier of cable communication systems with use of KT996A transistors and cross feedback is developed, has the following technical characteristics: strip of working frequencies (40-24 MHz; coefficient of strengthening of 39 dB; unevenness of the amplitude-frequency characteristic + 1,5 dB; maximum value of output voltage of 2 V; resistance of the generator and loading of 50 Ohms; supply voltage of 9 Century.