please help me, these complex, complicated circuits

[PG1995]

Hi

If you find that this query doesn't belong here, then please move it to the section you deem appropriate. Thank you.

I don't know every time I open an electronics book I get very much afraid after looking at those circuits. As an example have a look here:
**broken link removed**

How do you keep track of such complicated and complex circuits when solving them at school? What is your advice for me to overcome this fear? Sometimes, I simply slip into depression after looking at those circuits in the book. Please advise me what to do. When you were at school how you kept the track and solved the circuit. With simple circuits like this one:
http://gangles.ca/images/SimpleCircuit.jpg

It is fairly easy to imagine what's going on in the wires and how electrons etc. are moving. In other words one can create a mental picture for such a simple circuit. But what about those fearful circuits? Please help me.

 

[carbonzit]

I'll give you one clue to start you off:

You can reduce the complexity of that circuit by a factor of 2 right off the bat. How?

By realizing it's a stereo circuit, with two identical channels (left and right). Do you see that?

So right away it's only half as complicated as you thought it was. See how that works?

Like lots of other problems, they get solved by breaking them down into smaller, bite-size pieces that are easier to chew.

 

[Reloadron]

Did you learn how to walk before you were able to run?

First you need to understand the order of learning things, much like walking before running. The second circuit you posted is a very simple text book circuit designed as a learning tool. The circuit is designed to teach you to apply formulas and rules like Ohms Law and Kirchoff's laws as they pertain to voltage and current. Learning and gaining an understanding of electronics and electronics starts with the basics and fundamentals. They call them fundamentals as they are fundamentally important as to learning what comes next. You learn to play a musical instrument, you start with the basic fundamentals. You start at the beginning. The first circuit you posted is a circuit that is far more complex in design and operation than the second. Maybe this is because there are likely a few thousand circuits between the two? Once you understand the basic learning circuit and the rules and laws that govern it you move to a slightly more complex circuit, then many circuits later you look at a stereo amplifier circuit and easily identify it, what it does and how it does it. You start at the beginning.

The following is not intended to dissuade you but my own personal life experience. Since I am getting pretty old I can tell you this.

I am one of four children. My father was an electrical engineer, he had the analytical mind. My mother was well educated and an artist, she could also play musical instruments. She was quite good with piano and violin. My two sisters and my brother all seemed to have my mother's genes or whatever. My brother is an accomplished guitar player meaning he makes and writes music as well as teaching the arts at the university level. Both of my sisters are accomplished in the arts including music. However, they all will be the first to admit they lack the analytical mind to ever make a living at or learn electronics. Me? I took a few arts and music classes. Not going to happen, never going to happen. I can't master a musical instrument and never will. You could send me to music school for years and nothing but nothing will come of it. I am not intimidated by it, I am not afraid of it, I just can't do it. We have all been successful in our chosen career paths doing what we enjoyed doing.

Just My Take.....

Ron

 

[audioguru]

it doesn't matter which way the electrons move. Instead you need to learn about the function of the circuit blocks.

Didn't you learn anything about extremely simple opamp amplifiers??

 

[unclejed613]

so, let's begin with the second one, since it's a passive circuit (resistors, caps and coils are passive components, op amps, transistors and tubes are active components, and diodes are in a kind of active/passive twilight zone).

start by reducing the circuit to a single voltage and resistance:
first we solve for the 40 ohm resistor in parallel with the resistor string. 40||150=31.5 ohms or 1/((1/40)+(1/150))
then we solve the first string using the parallel combination R=20+31.5+20=71.5 ohms
next we need to find the total current 60/71.5=839mA

then we work back towards the load to find the current and voltage at the load:
next we want the voltage across the parallel string 0.839*31.5= 26.43V
next we want the current through the second string 26.43/150=176mA
and the voltage across the load is: 0.176*100=17.6V

that's how you work with circuits like that, first you simplify to a single voltage source and resistor, then work back to find the current, then the voltage at the load.

usually you spend a lot of time in basic electronics class working with problems like this one before moving on to other passive components and then active components. there are two basic "tools" used in circuit analysis, Thevenin's theorem, where you reduce a complex network to a voltage source and single resistance, and Norton's theorem, where you reduce the network to a current source and a resistor. it takes a bit of logical thinking and math to do this well, which is why so much time is spent teaching these methods. if you were to break down the analysis above, you would see application of both Tevenin's and Norton's theorems for various steps in the analysis, because sometimes i used a voltage source to find the answer to a step, then switched over and then used a current source to find an answer.

 

[simonbramble]

Further to AG's post, the first circuit block AC couples the input signal via capacitor C2, so any dc bias voltage that is applied to the + input of op amp IC1-a is not upset by any dc voltage that might be on the input signal. This is a standard trick. It just so happens that the + input of the op amp is clamped to ground by R4. Since the amp is powered by + and - supplies, R4 clamps the input to exactly half way between the 2 (0V), so you can get fully swing on your input signal before worrying about hitting the rails.

Now, you only really want to amplify the signal (ie the AC), not the DC, so if any dc voltage does sneak into the input of IC1-a, you dont want to amplify that too, so that is what C4 is doing. We know capacitors have an infinite resistance at dc, so C4 ensures that the first amplifier has a gain of 1 (1+33k/infinity) at dc, but its resistance goes down with increasing frequency, so C4 provides more of a short circuit to ground for the bottom end of R6, thus, at ac, you can consider C4 as being a short circuit - so you just have a gain of (1+33k/1k) - another simple circuit block...

It takes time to recognise these, but dont be put off. Keep plugging away and you'll get there!

 

[wkrug]

I think you should try to split the circuit into blocks.
The first Step ist to split it in 2 parts, because it is stereo.
Then you should try to split it into Basic circuits.
Like:
1 Circuit: IC1A, R8, R6, R4, C4 you get an non inverting Amp with a aplyfying factor of 34 with an Input Impedance of 1MOhm ( parallel with the input Impedance of IC1A).
C4 decreases the amplyfying factor for lower frequencies an DC.

2 Circuit: IC2A, R10, R12. Thats an inverting amp with an amp factor of 2 that is switchable in by S1A.

3 Circuit: IC3A, R15, R17, R19, R21 Thats an inverting amp with mixer (R15, R17) and an amp factor of 10. R21 is an "Fuse" resistor to avoid direct shorts at the output of IC3A.

4a The input: R1, C1, R3 - R1 and C1 give you a filter Function for the power supply. R3 is a load resistor, i think into the input should be connected a electred condensor micro that needs phantom power. C2 is a couple condensor to avoid DC at the Amp's input.

4b second input: R23a Thats only an additional input for higher levels.

5 Level: R14 is the level pot for the first input.

The single blocks are basic circuits, you need some experience to check that. But when you get that it will be quite easy.
So you should learn the basics and such an schematic in no more a problem for you.

I think the whole schematic is an microphone amplifier with micro phantom supply an an additional line input.

 

[audioguru]

The first simple circuit is a Noise-Cancelling Headphones project from the library at **broken link removed** . It has electret microphones glued to the outside of headphones.
If you want a detailed circuit description and instructions on how mto make it then look there.

 

[PG1995]

Hi

I offer my thanks to all of you for your suggestions and advices.

Best regards
PG