# Reading Circuit Diagram

## Main Question or Discussion Point

Hello all. This circuit diagram uses empty and full circles and also no circles. Is there a difference between a white circle in this diagram and a black one? I'm referring to the typical application diagram.

http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXqwvzw.pdf

Thanks.

Edit: Those are the pins on the IC. Nevermind. :-)

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## Answers and Replies

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jedishrfu
Mentor
the white circles signify the pins of the integrated circuit. They show the insides of the circuit and then a box with white circles for the pins and then the outside circuit. the black circles represent circuit connections.

There are also white circles in the switch these indicate contact points. wires that cross but don't connect use a little half circle to indicate one wire crossing over another wire.

Thanks jedi.

Next question is about connecting the signal inputs. If you look at pin 7 and 13 and 8 and 15 you see they are connected. I would read this to mean that the input voltages are combined with the supply voltages. This seems unusual. Am I reading it right?

Where do I connect the actual audio inputs in this diagram? At the black dots above the pin 7 and below pin 8? Not super clear to me.

If I'm not planning on using the mute or standby can I leave that part of the circuit out?

The squiggly circle on the left of the diagram - what is it?

Thanks again.

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AlephZero
Homework Helper
Thanks jedi.

Next question is about connecting the signal inputs. If you look at pin 7 and 13 and 8 and 15 you see they are connected. I would read this to mean that the input voltages are combined with the supply voltages. This seems unusual. Am I reading it right?
No, pins 7 13 8 15 are all poiwer supply pins, not input pins.

The chip has separate pin connections to poiwer the initial amplifier stages and the output stage. For a simple application like Fig 1 they can both be connected to the same power supply. If you look at the "High efficiency " circuit in Fig 18, you will see that the two pairs of power connections are different.

Where do I connect the actual audio inputs in this diagram? At the black dots above the pin 7 and below pin 8? Not super clear to me.
The audio input is is the "squiggly circle" (i.e. an AC voltage source). The input then gets to pins 2 and 3 on the chip.
If I'm not planning on using the mute or standby can I leave that part of the circuit out?
If you look at Figs 16 and 17 it is reconmended to use these to eliminate any noises (i.e. thunps and bangs in the speakers) at switch on.