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Hud-Bind Yin ‘By Feb. 25, 1958 HUO-BING YIN 2,824,964 SEMI-CONDUCTOR OSCILLATOR CIRCUITS‘ Filed June 28, 1955 OUTPUT INVENTOR. HUD-BIND YIN ‘BY A 7703 Ni V 2,824,964 United States atent O ” ice Patented Feb. 25, 1958 I 2 its organization and method of operation, as well as addi tional objects and advantages thereof, will best be under stood from the following description when read in con 2,824,964 nection with the accompanying drawing, in which: SEMI-CONDUCTOR OSCILLATOR CIRCUITS Figures 1 and 2 are schematic circuit diagrams of oscil lator circuits utilizing tetrode transistors and embodying Hue-Bing Yin, Collingswood, N. J., assignor to Radio two possible forms of the present invention. Corporation of America, a corporation of Delaware Referring now to the drawing, wherein like parts are Application June 28, 1955, Serial No. 513,469 indicated by like reference numerals in both ?gures, and 10 referring particularly to Figure 1, an oscillator circuit 6 Claims. (Cl. 250-36) embodying the invention includes a transistor 8, which may be considered to be an N-P-N junction transistor of the tetrode type. The tetrode transistor includes a semi conductive body 10, with which four electrodes are co~ This invention relates to electrical signal generator or 15 operatively associated in a well known manner. These oscillator circuits, and in particular to circuits of that type electrodes are designated, as is conventional, as an emitter utilizing semi-conductor devices, such as transistors as 12, a collector 14 and a ?rst and second base electrode 16 operative elements therein. More particularly, the pres and 18 which may be referred to as a normal base elec ent invention relates to oscillator circuits utilizing tetrode trode 16 and an auxiliary base electrode 18. The con transistors, that is, transistors having four electrodes. 20 struction and characteristics of transistors of this type in order to produce sustained oscillations by electrical have been described in an article by Wallace et al. in the means, it is necessary to feed back a portion of the out November 1952 issue of the Proceedings of the I. R. E., put signal from a signal amplifying device, whether it be starting on page 1395. While the tetrode transistor 8 an electron tube or a transistor, to the input circuit of the has been illustrated as being P type conductivity, it could device. To this end, many of the known oscillator circuits 25 also be of N type conductivity, that is, a P—N—P junction contain an external feedback path which couples signal transistor, so long as the polarity of the various required energy from the output circuit to the input circuit of the biasing voltages were reversed. amplifying device of proper phase and amplitude to sus The ?rst or normal base 16 of the transistor 8 is con tain continuous oscillation. nected directly to a point of reference potential or ground. In other oscillator circuits, a reduction in the number Alternatively, it could be connected through a suitable by of required circuit components and hence circuit simplicity passed resistor to ground. The auxiliary base 18 is con is achieved by utilizing the interelectrode capacitances of nected through .a suitable resistor 29 to the negative ter the signal amplifying device to provide the feedback neces minal of a source of direct-current biasing voltage, such sary for oscillation. In still other oscillator circuits, a de as illustrated by a battery 22, the positive terminal of vice having a negative resistance characteristic is utilized, 35 which is grounded. The resistor 2% and the battery 22 and by properly connecting a tuned circuit across the nega are bypassed by a capacitor 24 which is connected from tive resistance, sustained oscillation is achieved. This the junction of the auxiliary base 18 and the resistor 20 latter method has been utilized with success in oscillator to ground. circuits using point-contact transistors and also results Suitable frequency ‘determining means for the oscilla in circuit simplicity. For high frequency applications, tor circuit are provided by provision of a parallel resonant 40 however, such as those required for television receiving tank circuit 26 comprising an inductor 28 and a capacitor systems, for example, it is often di?icult to obtain high fre 30, which may be variable as shown for tuning the oscil quency oscillations with circuits which require but a mini lator circuit to the desired fundamental frequency of mum number of circuit components. operation. The upper or high ‘frequency end of the tank It is, accordingly, an object of the present invention 45 circuit 26 is connected as shown to the collector 14 of to provide an improved oscillator circuit utilizing a four the transistor. The lower end of the tank circuit 26 is electrode junction transistor. connected through a suitable radio frequency choke 32 It is another object of this invention to provide an im to the positive terminal of a source of direct current bias proved semi-conductor circuit for generating sustained ing voltage, such as illustrated by a battery 34, the nega relatively high frequency sine-wave oscillations and which 50 tive terminal of which is grounded. The choke 32 and the includes relatively few circuit components. battery 34 are by-passed by a capacitor 36 which is con It is yet another object of the present invention to pro nected from the junction of the tank circuit 26 and the vide an improved very high frequency oscillation genera choke 32 to ground. The generated oscillations may be tor utilizing a tetrode transistor, which may provide derived from any suitable point in the oscillator circuit. reliable operation with relatively simple circuit con 55 Preferably, they are inductively coupled from the induc-v struction. tor 28 of the tank circuit. To this end, an output wind These and further objects and advantages of the present ing 38 is provided which is inductively coupled to the in; invention are achieved by utilizing the negative resistance ductor 28 of the tank circuit 26. characteristic of the collector circuit of a tetrode transis As was mentioned hereinbefore, it has been discovered, tor. It has been found, in accordance with the invention, in accordance with the invention, that the collector cir that a suitable negative resistance characteristic can be ob 60 cuit of a tetrode transistor will exhibit a negative resist tained in a tetrode transistor by suitably biasing the nor ance characteristic over a portion of its operating range mal and auxiliary base electrodes of the device and open if suitable biasing voltages are applied to its normal circuiting the emitter electrode. This negative resistance and auxiliary base electrodes and its emitter electrode characteristic'may be effectively utilized to generate sus is open circuited. To most effectively utilize this nega tained oscillation. By capacitively coupling the emitter 65 tive resistance characteristic and to provide optimum cir directly with the collector, however, in accordance with cuit operation for the oscillator circuit, in accordance the invention, circuit'operation may be improved and with this invention, a capacitor having a small capaci very high frequency oscillations obtained. tance is used to couple the emitter of the tetrode tran ‘ The novel features that are considered characteristic of sistor with its collector. 70 Accordingly, in Figure l, a. this invention are set forth with particularity in the ap capacitor 40 is coupled directly between the emitter 12 pended claims. The invention itself, however, both as to and the collector 14 of the transistor 8. ’ 2,824,964 The capacitor 40, in a typical example, may have a ' trode, the combination comprising, means providing :a capacitance 'of from 2 to 4 micromicrofarads. By con ?rst sourceof energizing potential connected between necting the capacitor 4ti'as shown, that is, between the ‘ said auxiliary base electrode and said point-of reference ‘ emitter: and the collector; of the‘ transistor,: andibyu'sing potential, means connecting said norinalbase electrode to advantage ? the collector circuit"negativefresistance { of 5 with said point of reference potential, a frequency deterf ~ the transistor, 'it 'has been: found'ithat‘ high? frequency,‘ mining circuitconnected with said collector electrode, stable and sustained jsine-wav'ef ‘oscillations; of relatively» means providing, a secondsource of energizing poten- ' ' high amplitude may be generated. This is accomplished,’ tial connected between said frequency determining'cir moreover, by. a circuitiin which’ a minimum ‘number of» cuit and said ‘point of‘refere'nce potential, said inseam 71 circuit components are utilized and the. circuit' connec second sources of: energizing potential beingf'e?ective'toi Vtions therefor‘are relatively simple. A circuit inv accord-I 7. 7 applyrbiasing voltages solely to said collector, normal " ance with‘ithe' invention hasibee'ni'found moreover; to' base, and auxiliary base electrodes to providedawnega operate over a 'relatively' Wide range‘ of frequencies, tive resistance characteristic, in the collector circuit of’ _, 'i which'may be tuned by varying the capacity of the capac said tetrode transistonandv a 'coupling' capacitor’ con ' it'or?t). , In- addition, emitter biasing-is-"not required." nected between said emitter electrode and the junction]; ~ and it, has‘been‘ found that the required biasing voltages of said collector electrode and said frequency'determiné between‘ ‘the‘b‘ase electrodes of theftransis'tor'is less criti- " ing ‘circuit to ,enhanceljsaidlene'gative,
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