Transcript Bill Newman`s tests

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
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
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)
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)
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
t=30sec
t=0sec
Increasing time Total elapsed
about 2.5 mins
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
t=30sec
t=0sec
Increasing time Total elapsed
about 3 mins
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.
DHG SMS Card In 1401
Transistor Application
Biased so always active