My contribution to the increasing entropy, and eventual heat death of the universe
I’ve been learning more about different NPN transistor configurations and created the following diagrams for my own reference. The first shows where signal enter and exit the different configurations, but includes no current limiting. As such I’ve labeled the input and output signals I, for current. The second shows how current limiting might typically be introduced.
I’ve a long standing interest in STM projects since seeing the various low cost and amateur project attempts many years ago. I recently came across this paper describing a method for compensating for the probe vibration. The results (shown on HOGP below) see quite impressive. And allow for a scan rate of a few hundred Hertz.
Vibration compensation for high speed scanning tunneling microscopy
D. Croft and S. Devasia,
Rev. Sci. Instrum. 70, 4600 (1999)
I picked up a 6624A power supply the other day, it was going for about 20USD so I couldn’t resist it. The thing is a beast, 4 channels, 2 going to 50V, and 2 going to 20V. It can source 5A at 7V, 2A at 20V and 0.8A at 50V. And the thing is HUGE. I have to admit to being slightly scared of this thing (probably wise given how much voltage/current it can source).
Being a “system” power supply, it has no banana plugs on the front. I opened it up to see if I could add any. It does look like there’s space, but it certainly wasn’t designed for them to be fitted as an option. I’ll need to cut through the front metal shielding.
For some reason I’m reminded of pulling apart washing machines as a kid. This transformer is massive! I know why it’s so heavy now.
A few other pics. You can see that the channel modules are entirely separate the design varies significantly between the 20 and 50V channels.
I briefly checked the first channel, (set at 5V). Not too bad for 20USD:
I was curious to know what a transistor die looked like so I hacked the can off a 2N2222 and up it under my recently acquired microscope. The die image is above, I’m not sure if I cracked it opening the can or blew it up (it was suspect anyway). Interesting to note that it only has 2 wirebonds. I assume this means that the base is connected directly to the substrate which is P type material?
My name is Nava Whiteford. I’ve worked for a few sequencing companies. I have equity in a few sequencing companies based on my previous employment (I try to be unbiased in my posts). You can contact me at: [email protected]
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