TRANSISTOR OSCILLATOR FOR MULTIFREQUENCY PULSING 1317 



In the following sections the functions of a resonant ciicuil arc lirst 

 discussed. Then, the characteristics of a point contact transistor that 

 make it suitable for use in an oscillator are considered. This is followed 

 by a discussion of the behavior of the two when combined to form an 

 oscillator with consideration given to the effect various factors have on 

 performance. 



RESONANT CIRCUIT 



A resonant circuit has several properties of interest when one considers 

 it as part of an oscillator. These are: 



1. The input impedance of a parallel circuit consisting of an inductance, 

 L, and a capacitance, C, has the property of a resistance at approxi- 

 mately frequency,^ 



/o = wo/2t. 



That is, input impedance, 



where R = effective resistance of the inductor and 



when Q is high, Z = RQ^ = Rq the equivalent resistance at resonance. 



2. The decrement of a parallel resonant circuit when disconnected 

 from sources of power or loads is:^ 



[numerical decrement in cur-"" * 



rent or voltage per cycle 



When the effective resistance R becomes zero the decrement likewise be- 

 comes zero. 



In the oscillatory circuit considered the decrement is made zero by the 

 use of a negative resistance equal to the effective positive resistance of 

 the turned circuit. Additional loads on the turned circuit are accom- 

 modated in the same way. 



If the negative resistance in the simple circuit considered becomes 

 greater than the equivalent resistance of the tuned circuit and its 

 loads, power will be supplied by the tuned circuit at a rate that will 

 maintain equality between the power put into the circuit and the power 

 taken out. As a corollary to this, if the negative resistance is less than 

 the positive resistance, the voltage will increase across the circuit. For 



"1 = 1- e-2L/o . (1) 



