| 摘要 |
1286069 Gain control SINGER CO 3 Sept 1970 [3 Nov 1969] 42276/70 Heading H3T [Also in Division G4] An amplifier 46 (Fig. 3) used as an analogue/ digital converter (see Division G4) normally operates in a unit gain mode with two resistors 142, 143 switched into the feedback circuit. When a signal on lead 145 operates a field effect transistor switch 146 the gain of the amplifier is effectively converted to a gain of 32 since the feedback circuit is shunted to earth. Hot carrier diodes 140, 141 conduct only at a forward bias of 0À3 V. so that when the input is very small an effective open circuit occurs in the feedback loop to give a very high gain. |
