Electronics > Beginners
Some noob questions
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Mr. Scram:

--- Quote from: Mr D on August 18, 2018, 11:15:02 pm ---OK!

I'm not trying to understand the circuit, i'm trying to understand and make sense of the elements and general structure!

So is the circuit only missing the power supply to make it a complete, viable circuit?

--- End quote ---
Power supplies, plural. Most op-amps require a postive and negative supply. Have you checked out Dave's op-amp video? You might not understand all or even most, but it helped me when I was completely unfamiliar with what they are and how they work. Knowing the common configurations helps a lot when looking at schematics.

Mr D:
Haha, you're getting way ahead of me there! ;) (Mr Rstofer)

I'll check of Dave's vid.

OK, i need some more fundamentals filled out:

I understand how a simple circuit with a bulb works. It's a closed loop with a resistor (the bulb) converting energy into light, so the circuit is useful.

But if i imagine an oscillator, how does the oscillating voltage get on to the next part of the circuit? How does it move on to an amplifier, while still keeping the closed loop back to the negative battery terminal?

Or is induction used to have several closed loops of circuit communicate information (voltage difference) between each other while being part of a bigger schematic consisting of several such closed loops?
rstofer:
Vout is shown on your schematic and while I don't want to even think about the filters (the Z equations), at the end of the day, Vout is produced from the op amp  power supplies through a bunch of transistors inside the op amp.

So, Vout and Gnd (part of power supplies not shown) goes on to whatever comes next.

When I said +15 and -15V, those voltages are relative to something.  That something is the ground created where the two supplies get connected together to essentially create a 30V supply with a center tap to ground.

Vout is relative to ground (not shown).   But the op amp itself doesn't care about ground, doesn't need to know about ground and isn't connected to ground.  That's why op amp videos spend so much time on this fact.

Mr D:
Ok, so I guess a circuit is always a single interconnected network, with multiple ground points? So the goal is to start with a power source with a steady voltage difference and eventually output either light through a bulb, or audio via an oscillating voltage difference to a speaker, or information through a 8 seg LED, or whatever. But always there's the current running to ground after the bulb or speaker or 8seg display?

But then i don't see how such a complicated scheme could work. You change one resistor value somewhere and won't that have a knock-on effect thoughout the rest of the circuit?? How can this be manageable in a complicated circuit? Or are there ways to sandbox parts of the circuit against this sort of chaos?
Brumby:

--- Quote from: Mr D on August 18, 2018, 11:15:02 pm ---OK!

I'm not trying to understand the circuit, i'm trying to understand and make sense of the elements and general structure!

So is the circuit only missing the power supply to make it a complete, viable circuit?

--- End quote ---

To answer this question directly: Yes.

The actual power situation is also a bit obscure - with this describing what's around, but not shown:

--- Quote from: rstofer on August 18, 2018, 11:54:59 pm ---So, Vout and Gnd (part of power supplies not shown) goes on to whatever comes next.

When I said +15 and -15V, those voltages are relative to something.  That something is the ground created where the two supplies get connected together to essentially create a 30V supply with a center tap to ground.

Vout is relative to ground (not shown).

--- End quote ---

The only hint is the symbol at bottom left which indicates a connection to the "ground" point - which is the 0V point of the +15V / 0V / -15V power supply.  The +15V and -15V power connections to the op-amp are implied - because it is known that an op-amp will need some sort of power supply.  Also, the output (voltage) will be referenced to something - because it has to be referenced to something - and this is commonly the 0V point.


These connections are omitted in many cases to simplify the schematic, so that the important aspects of it - the signal path, biasing and so on - aren't cluttered by connections we know must exist.

Sometimes you will see the full set of connections for everything; sometimes you will see nothing of the power connections ... and sometimes you might have short lines going nowhere with labels, such as this:



While not explicitly shown those +12V points are connected together and go to the +12V point of the power supply.  Same for the -12V points.

Don't worry about the VSRC "battery".  That is just a way of showing an input voltage, often used in teaching situations.
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