PROPERTIES AND APPLICATIONS OF U-p-n TRANSISTORS 



531 



4. Power handling capacity and efficiency. The design can readily be 

 varied to permit the required amount of power dissipation up to at least two 

 watts. Furthermore the static characteristics are so nearly ideal that Class 

 A efficiencies of 48 or 49 out of a possible 50% can be realized. The efficien- 

 cies for Class B and Class C operation are correspondingly high. 



5. Ruggedness and small size. The germanium part of the , transistor is 

 enclosed in a hard plastic bead about ys inch in diameter. Inside the bead 

 three connections are mechanically as well as electrically fastened to the 

 germanium and are brought out as pigtails through the bead. This gives a 

 very sturdy unit. 



6. Freedom from microphonics. Vibration tests in the audio frequency 

 range indicate that these devices are relatively free from microphonic noise. 



7. Limited frequency response. Collector capacitance limits the frequency 

 response at full gain to a few kilocycles. By using a suitable impedance 



I BASE 



SINGLE- CRYSTAL 

 GERMANIUM BAR 



COLLECTOR 



Fig. 1 — The heart of an n-p-n transistor is a tiny bar of germanium to which three 

 mechanically strong electrical connections are made. 



mismatch it is possible to maintain the frequency response flat to at least 

 one megacycle while still obtaining a useful amount of gain. 



8. Operation with exceedingly small power consumption. Perhaps the most 

 remarkable feature of these transistors is their ability to operate with ex- 

 ceedingly small power consumption. The best example of this to date is an 

 audio oscillator which requires for a power supply only 6 microamperes at 

 0.1 volts. This represents 0.6 microwatts of power which contrasts sharply 

 with the million or more microwatts required to heat the cathode of an 

 ordinary receiving-type vacuum tube. 



Physical Appearance and Construction 



Figure 1 shows schematically the configuration of an n-p-n transistor. 

 The small bar of single crystal germanium contains a thin layer of p-type 

 interposed between regions of w-type. Mechanically strong ohmic connec- 

 tions are made to the three regions as indicated and brought out through a 



