| 摘要 |
855,985. Transistor oscillators. TELEFUNKEN G.m.b.H. Nov. 13, 1958 [Nov. 15, 1957], No. 36607/58. Class 40(6). A transistor oscillator, for very high frequencies at which the phase shift through the transistor is in the order of 90 degrees, comprises a tuned circuit and a back coupling coil connected in the reverse sense from a normal back coupling coil. The inductance of the back coupling coil is of such a value that it resonates with the effective capacitance of the transistor across it so close to the frequency of oscillation as to produce the necessary overall phase shift for oscillation generation. In Fig. 1 a transistor T connected in common emitter configuration has a tuned circuit 0 connected between the collector and earth. A back coupling coil L2 inductively coupled to the tuned circuit, is connected between the base of the transistor and earth and forms a further tuned circuit with the effective baseemitter capacitance CE of the transistor. In an alternative embodiment (Fig. 2 not shown) the oscillator is connected in a common base configuration and in another embodiment (Fig. 5 not shown) an oscillator of this latter type is modified as a mixer the input being fed into the base circuit. The coupling between the tuned circuit and the back coupling coil may be inductive (as shown in Fig. 1) mixed inductive and capacitive, or capacitors. Examples of circuits using capacitive back coupling are given in Figs. 6 and 7 (not shown). |
