| 摘要 |
1,074,577. Circuits using insulated-gate fieldeffect transistors. RADIO CORPORATION OF AMERICA. Dec. 11, 1963 [Dec. 17, 1962], No. 49020/63. Heading H3T. In a circuit in which an insulated-gate fieldeffect transistor is employed as an amplifier, oscillator or mixer, signals are applied both to the gate electrode and to a terminal connected to the substrate upon which the source and drain electrodes are formed. If the substrate is reverse biased with respect to both the source and drain electrodes, the substrate input has a high impedance and functions similarly to the gate electrode. Thus by con. necting the substrate and gate electrodes together, either directly, Fig. 6 (not shown), or through a capacitor, Fig. 8 (not shown), the maximtan value of the transconductance and its dependance upon bias voltages can be increased. If the substrate is forwardly biased with respect to the source electrode and reversed biased with respect to the drain electrode the device functions as a bipolar (i.e. junction) transistor whose transconductance can be varied by varying the potential applied to the insulated gate electrode, e.g. for A.G.C. Fig. 10 shows circuit of the type in which the substrate 148 of transistor 140 is reversely biased with respect to both source 142 and drain 144. The circuit operates as a reflex amplifier in a radio receiver, I.F. signals applied at 149 to the insulated gate being amplified by the transistor and taken off by transformer secondary 168. After demodulation, the signal is applied to terminals 153 for application to the substrate, the output being taken from across resistor 164. Fig. 15 shows a self-oscillating mixer circuit of the type in which the substrate-source electrode diode is forwardly biased. The circuit is equivalent to a transistor oscillator in which the collector (drain) circuit is back-coupled to the base (substrate) circuit to maintain oscillations, the oscillation level being modulated to effect mixing by the received signal applied to the insulated gate electrode. Figs. 9 and 14 (neither shown) illustrate mixer circuits which may be used for frequency changing or synchronous detection and in which independent signals are applied to the gate electrode and substrate and a combined output is taken from across a resistor connected in the drain circuit. |
