| 摘要 |
1,043,621. Circuits employing field-effect transistors. RADIO CORPORATION OF AMERICA. Feb. 19, 1964 [March 7, 1963], No. 6976/64. Heading H3T. An insulated-gate field-effect transistor is connected in series or in shunt with a signal path interconnecting a signal source and a load so as to serve as a controllable attenuator, the control being effected by a control voltage applied between source and gate electrodes. Fig. 6 shows a switching circuit interconnecting a source 84 and load 82, field-effect transistor 60 being connected in series in the signal path between the source and load and field-effect transistor 62 being connected to shunt the load. Oppositely varying signals are applied from a control-signal source 90 to the gate electrodes of the transistors. In Fig. 7 in which A.G.C. is applied to a R.F. amplifying stage 192 of a radio receiver both series and shunt attenuating field-effect transistors 178, 180 are provided, the oppositely-varying control voltages applied to their gate electrodes being derived respectively from the input to the base and the output from the collector of a PNP junction transistor 212. The A.G.C. voltage varying between O and - E 1 volts is applied to the base of transistor 212. |
