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Searching Google for a picture is difficult even with their new "similar image" functionality... While trying to understand an open collector pin's description on a schematic (for the TH72031, see page 7, pin 7), I found this symbol:

unknown circuit symbol

I know that two overlapping circles means a current source, but what does the "T bar" signify? Some sort of variability?

Thanks for any help!

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This is the figure referenced:

enter image description here

Also used on page 4:

enter image description here

That almost certainly means "trimmable" or "adjustable".

  • If it had an arrow head on the cross bar it would imply an adjustment that was potentially user (or service person) changed.

  • The T head usually means like a trim pot which is set for calibration purposes.

In this case it's inside the IC and you have no control over it (as far as I can see) - it may be LASER trimmed during manufacture? As you do not seem to be able to alter what it does it's not evident why they show it.

Here's an example of the T head used to show a trimpot adjustment.

enter image description here

Similar here but the T head is shown next to the resistor

enter image description here

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  • \$\begingroup\$ Well, that makes sense. Thanks! As you said, it's a mystery why they decided to show the adjustability. Meh. \$\endgroup\$
    – Rupert Swarbrick
    Commented Aug 26, 2011 at 0:44
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    \$\begingroup\$ I think in this case it means either the IC adjusts it automatically during operation or possibly trimmed during manufacture. The same diagram on page 7 (pin 3) has no adjust bar. Either way the user does not seem to have any control over it. \$\endgroup\$
    – Oli Glaser
    Commented Aug 26, 2011 at 6:00

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