| 摘要 |
1294108 Gain control S KUDELSKI 23 Dec 1969 [26 Dec 1968] 62713/69 Heading H4R The impedance across one diagonal AB of a bridge network of diodes 10, fed with a D.C. control current across the other diagonal, is used as the shunt element in an attenuator feeding an amplifier 13, in order to provide gain control and compensation for non linearity in, e.g. a magnetic recording system. As shown the gain control voltage is applied to terminals 17, and difference in the threshold voltages of the PNP and NPN transistors is provided by resistor 12. In an alternative method of supplying the D.C. control current, Fig. 4 (not shown), the bridge network is connected in series with one transistor of a long tailed pair whose total current is stabilized by constant current sources (X) arranged in the common emitter and common collector circuits of the pair, to provide control over a wide gain range. |
