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I'm interested in making the following resistor-divider circuit where I can tell 'POLL' to be high by my Arduino and then sample the voltage reading. The battery will have anywhere from 6-10volts. I have quite a few 2N2222A's on hand and I was wondering if I could use it as Q1 as the voltage specification says 40v 500mA (I don't expect a load to be on this), similarly, I was wondering if I could use J176 as M1 or if there are other options? Due to size constraints I'm trying to use all TO-92 packages.

Schematic

J176:

This device is designed for low level analog switching sample and hold circuits and chopper stabilized amplifiers.

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  • \$\begingroup\$ What's the reason for not just using 2 resistors? \$\endgroup\$ – Wesley Lee Oct 22 '16 at 23:18
  • \$\begingroup\$ This way the resistor-divider turned on when in use to minimize battery loss. It only needs to be polled every minute or so... \$\endgroup\$ – Alex Oct 22 '16 at 23:31
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    \$\begingroup\$ Ok, but is this really worth it, to save 250uA? (10V / 40kOhm) \$\endgroup\$ – Wesley Lee Oct 22 '16 at 23:34
  • \$\begingroup\$ @WesleyLee well, it is a battery, so almost surely yes it is worth it. \$\endgroup\$ – Spehro Pefhany Oct 23 '16 at 13:03
  • \$\begingroup\$ @SpehroPefhany -- I mean, if he is using Arduino there are many easier ways of saving much more energy. \$\endgroup\$ – Wesley Lee Oct 23 '16 at 17:37
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The 2N2222 is fine, but the J176 is a p-channel JFET and not what you want (it will be 'on' all the time in this circuit- until you turn the 2N2222 on, after which it and the 2N2222 will both be fried).

Try a BSS84 for the p-channel MOSFET, or maybe a BS250 if you insist on using bulky through-hole parts.

The datasheet for the J176 is a little remiss in not telling you exactly what it is or using a schematic symbol anywhere at all.

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  • \$\begingroup\$ don't make fun of through-hole... they are easy to solder! ;) \$\endgroup\$ – Alex Oct 28 '16 at 9:19
  • \$\begingroup\$ @Alex Available choices will be severely constrained if you limit yourself to through-hole, in many cases. \$\endgroup\$ – Spehro Pefhany Oct 28 '16 at 9:23
  • \$\begingroup\$ understandable, I just don't have the necessary equipment to micro solder \$\endgroup\$ – Alex Oct 28 '16 at 9:36

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