What is this component on a circuit diagram? - Page 1
Forum section: electronics / beginners

author: SlowBro
author_rank: Regular Contributor
timestamp: March 15, 2018, 01:57:21 pm
content: I'm looking at a datasheet for a L293 and I see on the chip equivalent diagram some strange double ring component. The prefix is G*. Please see the attached. What am I looking at?Here is the datasheet. Page 3.http://www.st.com/content/ccc/resource/technical/document/datasheet/3f/2a/59/15/61/43/45/af/CD00000058.pdf/files/CD00000058.pdf/jcr:content/translations/en.CD00000058.pdf

author: ion
author_rank: Regular Contributor
timestamp: March 15, 2018, 02:04:24 pm
content: I believe that represents a current source.

author: OE2WHP
author_rank: Regular Contributor
timestamp: March 15, 2018, 02:42:58 pm
content: A transformer or generally a Voltage converter.https://www.petervis.com/electronics/Transformer_Symbol/Transformer_Symbol.html

author: Cerebus
author_rank: Super Contributor
timestamp: March 15, 2018, 02:46:06 pm
content: Quote from: OE2WHP on March 15, 2018, 02:42:58 pmSorry, no. The previous poster is correct, it is a (constant) current source.

author: Brumby
author_rank: Unknown
timestamp: March 15, 2018, 02:50:38 pm
content: Quote from: Cerebus on March 15, 2018, 02:46:06 pm+1.The link given does say it is an alternate symbol for a transformer - but I don't agree with that AT ALL.

author: OE2WHP
author_rank: Regular Contributor
timestamp: March 15, 2018, 03:07:32 pm
content: hmm...got this out of an IEC standard. This symbol is used for transformers (at least in EU). The constant current source would show an arrow and the Letter I next to it. Also Australian standard AS 1102.106 shows this as transformer...But you are probably right that this is not true outside of IEC teritory.

author: free_electron
author_rank: Super Contributor
timestamp: March 15, 2018, 03:24:06 pm
content: the letter G is a dead giveaway ... Voltage controlled current source. This comes from Spice ... this schematic is an internal schematic from an opamp.

author: ArdWar
author_rank: Frequent Contributor
timestamp: March 15, 2018, 03:34:43 pm
content: That's old DIN-style current source symbol, and likely not an actual component too.It's a internal IC "schematics", manufacturers usually simplify things a lot, not actually drawing every bit of it true to the actual construction. Use "shorthands" or combined symbols. Use generic (but representative) component representation of a rather complex circuitry, especially a proprietary one.

author: Cerebus
author_rank: Super Contributor
timestamp: March 15, 2018, 03:43:05 pm
content: The other dead giveaway is that it is in the tail of a differential pair. Even if in some benighted corner of standards land it is an acceptable symbol for a transformer, the job it is doing makes it very clear that it is a constant current source. Probably cooked up by the same people who use a little rectangle for a resistor and for an inductor they use, an identical little rectangle.

author: dmills
author_rank: Super Contributor
timestamp: March 15, 2018, 04:14:27 pm
content: The transformer interpretation comes from the big power guys when drawing diagrams of transmission and distribution networks (Which are generally single line drawings), it is one of those Electrics vs Electronics things.It is a current source (actually a sink in this instance I think), very standard in the emitter lead of a long tailed pair.Regards, Dan.

author: David Hess
author_rank: Super Contributor
timestamp: March 17, 2018, 04:57:08 am
content: It is a current source probably implemented as some variation of a current mirror. Not shown is a likely reference connection to the bias control circuits referenced to the positive supply in this case.