| 摘要 |
<p>The principles of "linear amplifier circuits for direct current and alternating current" have been known for a long time and are partly derived from the valve techniques. The type which is most commonly used at present comprises a differential input and a final push-pull stage and operates with a counter-coupling. The final transistors operate usually as emitter-followers at the dynamic operation point A-B. This principle requires that the voltage amplifier reaches the voltage amplitude of the output voltage. In the new "linear amplifier circuit for direct current and alternating current", the final transistors (T3, T4) operate as a common emitter at the dynamic operation point B-C and the currents thereof are coupled. The voltage amplitude of the voltage amplifier (OP) has no importance since said voltage allows only the flow of a current to zero. Said current, however, flows from the positive or negative side in the voltage amplifier (OP) and simultaneously controls the final transistors (T3, T4). In case of a small signal or without the latter, the output voltage (U-aus) is generated by two pretransistors (T1, T2). These also operate as a common emitter and their currents are also coupled. The output voltage is obtained from the difference of the collector currents of the push-pull transistors (T1, T2, T3, T4). Said voltage is counter-coupled to the differential input amplifier (OP) and is thus adjusted at a fixed ratio to the input voltage. As the voltage amplitude is smaller at the output (U-aus) of the voltage amplifier (OP) than the input voltage, its open loop amplifier is exclusively used to compensate for the non-linearities of the amplifier. Even the output load has no influence on the output voltage. As the voltage amplitude of the voltage amplifier is only a few volts, the voltage amplifier may be a conventional operational amplifier which is commercially available, even in the case where the output voltage of the final stage is high. Due to the dynamic operation point B-C of the final transistors (T3, T4), the ratio between the output power and the dissipated power is very advantageous, of the order of 3/1. This new principle enables the construction of better linear amplifiers with a reduced number of component parts.</p> |
