H. C. Lin

Oral History – H. C. Lin


Oral History – H. C. Lin



I think some of your early patents related to stabilizing transistor circuits, especially in audio amplifiers. 

That’s right.   If I did make any contributions to early transistor technology, then my study of the temperature effect was one.  In the early days, when we tried to bias transistors in the same way as was done for a vacuum tube, it wouldn’t work.  You see, the heater for the tube keeps the internal temperature pretty constant, but in the transistor, the temperature depends on the ambient temperature, which can vary widely. 


As a matter of fact, I built a 20 watt amplifier and took it to my boss to demonstrate, and took it outside where it was cold – it wouldn’t work.  Another time, it overheated in use, and wouldn’t work.  On the original 20 watt, I played music through a loud speaker.  I only needed one amplifier for monaural, because stereo was just coming out then.  That amplifier really was one of my favorite circuits, because I used the so-called “Quasi- Complementary” design.  I got a patent on this design and it is widely used today. You see at that time, we only had PNP (power) transistors, and these were all germanium.  Sziklai had just patented the complementary symmetry circuit (using both NPN and PNP), but we couldn’t get any good NPN (power) transistors, so that is why I developed the quasi-complementary. I think that this (circuit) is another contribution I made to transistor development. I published this circuit in Electronics magazine in 1956.  



Go To Lin Oral History, Page 4





The top photo is from the 1956 RCA publication entitled “TRANSISTORS 1”.  This is a classic text summarizing mid-1950s transistor technology that featured dozens of articles by RCA scientists and engineers, including an article by Dr. Lin on the 20 watt  audio amplifier shown here.  The lower photo shows the types of transistors available at the time, including two black units (SX155A power transistor and 2N109 preamp) that were used in the original 20 watt amplifier.  The white epoxy TA153 is an example of an original germanium developmental type from RCA.  All these transistors are germanium PNP types - there was considerable difficulty in producing NPN germanium power types and Dr. Lin’s work on the quasi-complementary amplifier allowed good performance with only PNP germanium power transistors.    



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