| 摘要 |
<p>1,057,308. Automatic gain control circuits. ALBISWERK ZURICH A.G. Aug. 4, 1964 [Aug. 23, 1963], No. 31263/64. Heading H3T. In an automatic gain control circuit for an amplifier the control voltage derived from a detector D is fed to the base of a first transistor T1, having its emitter connected to the emitter of a complementary transistor T2 the base of which is connected to a fixed or variable reference potential and the collector of which supplies a control signal for one of the amplifier stages. As shown, the control is effected on stage V2 by varying the resistance of clamping diodes G1, G<SP>1</SP>2 and control is effected of stage V3 in a similar way from the collector current of T1. For testing purposes the link C1 may be broken without affecting the control signal applied to V3. A number of stages may be controlled from T2 via individual amplifier stages (Fig. 2, not shown) having variable emitter resistors (T21-T23) or, for modulation compression circuits, a non-linear emitter impedance network (G22, G23). The load of T2 may include a diode (G21) to compensate for the input impedance of the amplifiers and in Fig. 3 (not shown) transistor pairs (T31, T32) are used as the amplifiers, one amplifier including an LC filter to slow down the rate of change of control voltage as required when pulse radar signals are being amplified. In Fig. 4 (not shown) a fast-acting circuit is provided and a meter may be switched into the collector circuit of T1.</p> |
