440 THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1952 



Fig. 32— Packaged oscillator and amplifier using junction transistors. 



only the available undistorted power output increasing as the voltage is 

 increased. At a collector voltage of 1.5 volts it draws a collector current 

 of approximately 0.5 ma per unit for a total power drain of 1.5 milli- 

 watts. Under these conditions it will deliver Class A power output of 

 about 0.7 milliwatt. The noise figure of such an amplifier has been 

 measured to be in the range from 10-15 db at 1000 cps depending upon 

 the operating biases. 



To the left of Fig. 32 is shown a small transistor audio oscillator having 

 a single M1752 transistor, a transformer and one condenser. To see just 

 how little power was the minimum necessary to produce stable oscilla- 

 tions such an oscillator was tried at increasingly lower collector supply 

 voltages. It was found that stable oscillations could be maintained down 

 to collector supply voltages as low as 55 millivolts and collector current 

 as low as 1.5 microamperes for a total drain of 0.09 microwatt. 



SUMMARY 



With respect to reproducibility and interchangeability, transistors 

 now under development appear to be the equal of commercial vacuum 

 tubes. 



With regard to reliability, transistors apparently have longer life and 

 greater mechanical ruggedness to withstand shock and vibration than 

 most vacuum tubes. With regard to temperature effects, transistors are 

 inferior to tubes and present upper limits of operation are 70-80°C for 

 most applications. This restriction is often reduced in importance by 

 the lower power consumption which results in low equipment self- 

 heating. This, however, is the outstanding reliability defect of transistors. 



