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The attached screenshot is from a schematic in a datasheet. I know that the flat-topped arrow is a diode, but I don't know what the pair of looped circles are. Can anyone help me out? If there's a good online symbol reference, please share the link!

unknown symbol

Thanks!

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I believe that would be a diode (the triangle and horizontal line) in series with a current source (the two circles).

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The two circles are DC Current power Source

http://electricalwhat.com/power-source/dc-current/

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  • \$\begingroup\$ electricalwhat.com/diodes/junction \$\endgroup\$
    – endolith
    Commented May 17, 2010 at 14:11
  • \$\begingroup\$ It can also be used for an AC constant current source. The SPICE simulator I use has both DC and AC current sources using that symbol. \$\endgroup\$
    – Leon Heller
    Commented May 17, 2010 at 14:47
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    \$\begingroup\$ @LeonHeller: Isn't "AC constant current" a contradictio in terminis? If it's AC it can't be constant. I've never seen AC current source IRL either. \$\endgroup\$
    – Federico Russo
    Commented May 7, 2012 at 15:29
  • \$\begingroup\$ @FedericoRusso An AC constant current source marked \$I\angle\theta \$ usually means that the current in the direction of the arrow is a phasor of magnitude \$I\$ and phase \$\theta\$, that is, the current is \$I\cos(\omega t + \theta)\$, regardless of the impedance into which the current is flowing. It does not mean that the current has constant value for all time as in a DC current source, but rather that the amplitude and phase (and of course the frequency) of the sinusoidal current flowing through the device is independent of the impedance to which it is connected. \$\endgroup\$
    – Dilip Sarwate
    Commented Jun 12, 2012 at 16:14
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A diode in series with a constant current source.

There was a symbol guide published by the ARRL at http://www.arrl.org/qst/qs4hd.pdf but that link appears to be broken :(

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Like jluciani says it's a constant current source, and therefore DC. The proper symbol has an arrow next to it or inside it to indicate the current direction.

enter image description here

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In IEC-land (Europe and the Commonwealth), two overlapping circles usually means an (AC) transformer.

From Australian Standard AS 1102.106 Graphical symbols for electrotechnical documentation - Part 106: Production and conversion of electrical energy:

enter image description here

Where the transformer is a three-phase type, there are often some extra qualifying symbols added which denote the vector groups of the windings.

enter image description here

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