30 watt a.f output stage - based on a new hybrid IC

The input of the device is formed by dif- ferential amplifier T2/T3 whose emitter resistance consists of current source Tl/D1/D2. The output of the amplifier is fed to driver T6 whose collector resist- ance is formed by current source T4. Transistor T5 provides a constant bias volt- age for the output transistors: the bias allows a quiescent current of about 50 mA through these transistors. The output tran- sistors are arranged as quasi-complemen- tary darlingtons: T7 and T9 form an n-p-n darlington; T8 and Tl0 are the com- plementary pair. Any asymmetry of T8/T10 is negated by diode D5. Circuit description The amplifier circuit, shown in figure 2, is designed for operation from a + 25 V symmetrical power supply. The full 50 V, decoupled by C4 and C8, is applied to the output transistors, pins 6 and 8, in the STK077. The supply for the input and driver stages is decoupled by R3/C3 and R5/C7 respectively and applied to pins 10 and 4. Feedback is arranged by connec- ting the output,...