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Loopy Transistor Study

Loopy Transistor Study. PNP Germanium Transistors from 1401 project. From SMS card DHG (see last slide), identified as having a slow fall time. Test setup. Loopy Frequency Dependence.

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Loopy Transistor Study

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  1. Loopy Transistor Study PNP Germanium Transistors from 1401 project. From SMS card DHG (see last slide), identified as having a slow fall time. Test setup

  2. Loopy Frequency Dependence IV character versus scan rate when setting Ib = 30 uA. Horizontal excursion is 0 to 4V, vertical is 0 to 250uA. 20 KHz 5 KHz 500 Hz 50 Hz 5 Hz ‘DC’ - .125 Hz

  3. Slow Speed Loop Details Manual scan of Vce done with power supply knob (0 to 4V). Ib = 30uA. Long persistence on storage scope. Scan from bottom to top in .5 seconds (Vce 0V to 4V) Slow scan .125 Hz Scan from top to bottom in .5 seconds (Vce 4V to 0V)

  4. Slow Speed Loop Details More manual scans of Vce done with power supply knob (0 to 4V). Ib = 30uA. Long persistence on storage scope. Manual scans 5x faster than previous slide. Scan from bottom to top in .1 seconds (Vce 0V to 4V) Scan from top to bottom in .1 seconds (Vce 4V to 0V)

  5. Low Speed Loop Temperature Dependence Transistor received a 1 second shot of circuit cooler. Scan rate is 50 Hz. Total Vce excursion is 4V. Pre cooler curve t=150sec t=120sec t=90sec t=60sec Increasing time Total elapsed about 2.5 mins t=30sec t=0sec

  6. High Speed Loop Temperature Dependence Transistor received a 1 second shot of circuit cooler. Scan rate is 15KHz. Total Vce excursion is 4V. Pre cooler curve t=150sec t=120sec t=90sec t=60sec Increasing time Total elapsed about 3 mins t=30sec t=0sec

  7. Loopy Transistor Observations • DC character is not loopy, although must get to very slow rates before this happens (4 seconds for 0 to 4 volt sweep) • Increasing Vce curve is more ‘normal’ than decreasing Vce curve. Decreasing Vce curve is “flatter”. Appears that the loop ‘opens up’ starting at about .3 hz, with the increasing side dip dropping down, and the decreasing side dip moving up. • Loopy behavior is highly temperature dependent. • Loopy behavior is changes versus frequency. From DC to 20KHz, no loop behavior is seen from 500Hz to 5KHz.

  8. DHG SMS Card In 1401 Transistor Application Biased so always active

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