TRANSISTOR OSCILLATOR FOR MULTIFREQUENCY PULSING 1323 



AMPLITUDE 

 WITH RESISTANCE 



TRANSISTOR 



1729 TYPE 



E1459M 



Figs. 5 and 6 — Oscillograms showing the relationship of collector current to 

 collector voltage during a complete cycle for several operating conditions. Fig. 

 5 (left) is a multiple exposure made to illustrate the ability to oscillate at a lower 

 output level with decreased feedback. This is due to the much higher alpha ob- 

 tained with low emitter currents. Fig. 6 is for normal operating conditions. 



This increase in voltage is however very small since the losses will increase 

 as the square of the voltage and the rate at which energy is supplied to 

 the circuit will decrease. The decrease in rate is due to the change from 

 a negative resistance to a positive resistance in region 3. This causes the 

 average negative resistance for the complete cycle to have a higher value. 



Feedback which is far greater than is required can in some cases cause 

 the peak value of the ac voltage to exceed the dc voltage. Power is drawn 

 from the energy stored in the tank circuit when this occurs. This effec- 

 tively limits any further increase in output voltage. 



A change will also be introduced in the emitter circuit due to opera- 

 tion in region 3. That is, the voltage feedback introduced in the emitter 

 circuit by collector current flowing in the common base resistance is re- 

 versed in phase in region 3.^ This is due to a reduction in collector current 

 when the voltage applied to the emitter circuit is still rising. This feed- 

 back is sufficient in many cases to cancel the increase in emitter voltage. 

 The emitter current in such a transistor will therefore remain nearly 

 constant in this region. In region 2 however the feedback is in such a 

 direction as to aid the flow of emitter current. The result is that the 

 voltage drop across the emitter resistance is approximately canceled by 

 the voltage across the base resistance. Due to this relationship the tran- 



