PRESENT STATUS OF TRANSISTOR DEVELOPMENT 



435 



Fig. 26 — Performance progress. 



For high-sensitivity low-noise appHcations, the point-contact devices 

 have been improved to have noise figures of only about 40-45 db, whereas 

 the Ml 752 n-p-n transistor has been shown to have noise figures in the 

 10 20 db range. All such noise figures are specified at 1000 cps and it 

 should be remembered that they vary inversely with frequency at the 

 rate of about 11 db per decade change in frequency. 



For video, I.F., and high-speed switching applications, measurable 

 improvement has been attained in the frequency response. For video 

 amplifiers up to about 7 mc, the M1729 point-contact transistor is 

 capable of about 18-20 db gain per stage. For high-freciuency oscillators 

 and microsecond pulse switching, the M1734 point-contact transistor is 

 under development. Preliminary models of 24 mc I.F. amplifiers using 

 the ^11734 have been constructed in the laboratory, these amplifiers 

 having a gain of some 18-24 db per stage and a band-width of several 

 megacycles. However, more work needs to be done on the ]\11734 to 

 reduce its feedback resistance. For pulse-handling functions, such M1734 

 units work very nicely as pulse generators and amplifiers of | micro- 

 second pulses, requiring only 6-8 volts of collector voltage and 12-20 

 mw of collector power per stage. The amplified pulses can have ampli- 



