| 摘要 |
1521733 Automatic voltage control SIEMENS AG 31 July 1975 [22 Aug 1974] 32017/75 Heading G3R The sinusoidal output voltage of a transistor amplifier is regulated by rectification and comparison with a reference in a differential amplifier, the output of which is connected to the input of a second stage of the amplifier. The first stage of the amplifier receives a rectangular voltage signal, in the absence of which the first stage is conductive but the second stage is blocked to minimize current consumption. As shown in Fig. 1, a two-stage amplifier T1, T4 receives a rectangular signal through a resistor R2 and capacitor C2. The signal may be 12 KHz pulses applied directly, or 4 KHz pulses derived from the 12 KHz signal by two flip-flops and a NOR-gate IC2. The amplified rectangular signal is supplied to a transformer circuit Ul, tuned to produce an undistorted sinusoidal output, a sample of which is rectified by a diode D3 and fed via a resistor R9 to one transistor T3 of a differential amplifier, the other transistor T2 of which is biased by a Zener diode Dl. When this Zener reference voltage is exceeded by the sample output voltage, a correcting voltage is applied to the base of the second stage transistor T4 in order to regulate the output voltage. A filter transistor T5 provides harmonic suppression in the operating current supply. |
