Just go from the base (input) to the collector or sometimes the emitter (output). In this case there are two paths, one for + signal, and one for - signal.
This one is more difficult, and there are many extra devices for current sources and current mirrors. Start with a simpler discrete design.
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Be aware that 'signal path' can be both a helpful concept and a seriously misleading concept. The quick answer is to start from the input and work towards the output. In a complicated circuit you may also need to start from the output and work back towards the input. Ideally these two paths will obviously meet somewhere, but in a complicated circuit they may appear to miss each other - especially if there are two signal paths which diverge then meet up again.
It may help to remember that a BJT/FET base/gate is unlikely to be an output, and a BJT/FET collector/drain is unlikely to be an input.
In a DC-coupled circuit it can be difficult at first glance to distinguish between bias circuitry and signal-handling circuitry. This is partly because the distinction is one we make for our benefit; the circuit just obeys the rules of physics, and physics does not distinguish between bias and signal.
It may help to remember that a BJT/FET base/gate is unlikely to be an output, and a BJT/FET collector/drain is unlikely to be an input.
In a DC-coupled circuit it can be difficult at first glance to distinguish between bias circuitry and signal-handling circuitry. This is partly because the distinction is one we make for our benefit; the circuit just obeys the rules of physics, and physics does not distinguish between bias and signal.
I would make a suggestion after determining the input and output trace backwards from a forced intended output to what the conditions must be at each node to "make it so" all the way back to the input. The other way around for most high gain circuits will soon hit a limit.
Look at some Japanese amp circuit diagram from their service manual. They usually indicate the signal path by a thicker line.
You can do it that way. You will be able to figure it out yourself by looking at an example.
You can do it that way. You will be able to figure it out yourself by looking at an example.
The internals of an opamp are probably not a good example for someone learning the basics imo. There's a lot going on in there, lots of "basic" building blocks all of which interconnect, but you need to be able to recognise those and just as importantly, have some idea how they behave.
My advice would be to start with simple one and two stage amps and really get to grips with how they work... and then progress to more complex configurations.
My advice would be to start with simple one and two stage amps and really get to grips with how they work... and then progress to more complex configurations.
I suggest learning some of the basic building blocks used in discrete circuit design or integrated circuit design. Once you can recognize a differential pair, cascode, and the three common single-transistor amplifier stages, you can break the circuit, such as the NE5532 into blocks and find the signal path (or paths) that way.
Sedra/Smith, "Microelectronic Circuits" would be a good place to start. I've linked to the most recent edition. The older editions are just as useful and can be had for much less on the used market.
~Tom
Sedra/Smith, "Microelectronic Circuits" would be a good place to start. I've linked to the most recent edition. The older editions are just as useful and can be had for much less on the used market.
~Tom
I find lampizators opinion about signal path quite interesting:
HERESY No 1. SIGNAL PATH
I read about signal path so many times I am almost ready to believe it. Short signal paths, pure s.p., elegant s.p. silver wire in s.p. you name it. I am sure everybody knows what I am talking about.
The bitter truth is IT IS NOTHING LIKE what people think it is. The so called "signal" does not flow along some PATH. Lets take a pre amp for an example. The signal (current) enters via RCA jack, and the first thing it sees is usually a parallel resistor or some kind of parallel pot. The signal sinks to the ground through this resistor and that's all. Yes. The journey is over. It is like the movie hero who dies in the first scene. Hard to believe?
Having said that - lets agree once and for all - the CURRENT flows, and the VOLTAGE IS. The voltage does not flow.
The Waves PROPAGATE in circuits but they happen everywhere at the same time and involve all circuits.
The minuscule current flowing from your CD source to the ground via this parallel impedance of a mentioned pot produces small voltage resulting from the impedance of the pot (Ohm's law) This voltage is then being "read" by the grid electrode of the tube, or in non-hifi units - the base of transistor, and this signal in turn regulates the series impedance of the active element. The electricity from power supply then copies the original signal in what we call "amplification stage". So this is a copy, not the original. Signal path is a myth. The VOLTAGE - does not flow by definition. The voltage IS. The current flows. But it does not flow from source to the load (receiver). The current flows from power supply to the ground via active elements. In every STAGE of amplification the current flows in VERTICAL manner, not "horizontal". If an amp has 3 stages, there will be 3 cases of current flowing from PSU to ground by the active part. So path is from PS to ground, not from CD to speakers. Once we understand it - it is easier to talk further.
Another thing is timing of signal - it does not go from one place to another. The WHOLE CIRCUIT responds to signals instantly, the whole event HAPPENS. It does not flow. The circuit response is everywhere at the same time, all elements at the same time. No flow. Input receives - output responds. At the same moment.
HERESY No 1. SIGNAL PATH
I read about signal path so many times I am almost ready to believe it. Short signal paths, pure s.p., elegant s.p. silver wire in s.p. you name it. I am sure everybody knows what I am talking about.
The bitter truth is IT IS NOTHING LIKE what people think it is. The so called "signal" does not flow along some PATH. Lets take a pre amp for an example. The signal (current) enters via RCA jack, and the first thing it sees is usually a parallel resistor or some kind of parallel pot. The signal sinks to the ground through this resistor and that's all. Yes. The journey is over. It is like the movie hero who dies in the first scene. Hard to believe?
Having said that - lets agree once and for all - the CURRENT flows, and the VOLTAGE IS. The voltage does not flow.
The Waves PROPAGATE in circuits but they happen everywhere at the same time and involve all circuits.
The minuscule current flowing from your CD source to the ground via this parallel impedance of a mentioned pot produces small voltage resulting from the impedance of the pot (Ohm's law) This voltage is then being "read" by the grid electrode of the tube, or in non-hifi units - the base of transistor, and this signal in turn regulates the series impedance of the active element. The electricity from power supply then copies the original signal in what we call "amplification stage". So this is a copy, not the original. Signal path is a myth. The VOLTAGE - does not flow by definition. The voltage IS. The current flows. But it does not flow from source to the load (receiver). The current flows from power supply to the ground via active elements. In every STAGE of amplification the current flows in VERTICAL manner, not "horizontal". If an amp has 3 stages, there will be 3 cases of current flowing from PSU to ground by the active part. So path is from PS to ground, not from CD to speakers. Once we understand it - it is easier to talk further.
Another thing is timing of signal - it does not go from one place to another. The WHOLE CIRCUIT responds to signals instantly, the whole event HAPPENS. It does not flow. The circuit response is everywhere at the same time, all elements at the same time. No flow. Input receives - output responds. At the same moment.
Already trying to introduce the aspect of a control loop huh? 🙂 This is exactly how I first began to understand the workings of an amplifier circuit, going by what the nodes are supposed to be at a given state as a result of what the circuit 'wants' them to be. (p.s. I bow in humbleness to your expertise
)Yes, it's really not a solid "path", it's usually a complex network of current loops coupling to each other in some manner.
However, at various points in circuit we can indeed locate "nodes", which in some form, whether voltage or current, convey information of our "signal" waveform. In most cases you can figuratively speaking "connect the dots" and follow a "path" that conveys the signal through the circuit.
But in the end it really doesn't work like that because that "path" is really just a collection of current loops, each introducing their own unique interferences, distortions and such, in many cases rather interactively as well.
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Reopened as requestedThe path does indeed get quite complicated in some circuits, especially symmetric/differential ones - best to start with a classic 3-stage amp circuit and the path is less confusing - note with feedback there are two basic paths, non-inverting input to output and output to inverting-input (the feedback network).
With class B the forward path splits at some point to the drivers, but it can be thought of as one path that switches on each half-cycle.
A path will lead from say input to output without side-arms (in other words ignore parts that go off to the rails or ground, they are not "on" the path).
Opamp circuits are usually very easy to trace too.
In the classic 3-stage circuit the path goes from input pair to VAS to drivers to outputs, the feedback path is just a passive network from output to input pair - easy to add to a diagram with highlighter pen for instance.
If any of the signal paths is broken in an amp the output will slam to the power rail or some random output voltage, no longer influenced by the input - removing components not on the path may influence the output in various ways of varying impact.
Its much easier in RF design to trace the path as its usually in stripline or microstrip...
With class B the forward path splits at some point to the drivers, but it can be thought of as one path that switches on each half-cycle.
A path will lead from say input to output without side-arms (in other words ignore parts that go off to the rails or ground, they are not "on" the path).
Opamp circuits are usually very easy to trace too.
In the classic 3-stage circuit the path goes from input pair to VAS to drivers to outputs, the feedback path is just a passive network from output to input pair - easy to add to a diagram with highlighter pen for instance.
If any of the signal paths is broken in an amp the output will slam to the power rail or some random output voltage, no longer influenced by the input - removing components not on the path may influence the output in various ways of varying impact.
Its much easier in RF design to trace the path as its usually in stripline or microstrip...
What is understood as a signal path also depends on the "templates".
Most audio circuits end up as signal loops (feedback) - a simple front in - back out cannot be defined. These correction, control loops serve to suppress swing (electrical circuits are also swing systems, comparable to mechanical ones such as piano strings and piano)
Aside:
The sonic influence of components does not only occur as part of the idealized signal path. A capacitor with, for example, a "delicate and colorful sound character" influences the sound of a device at any point to the same extent, whether as a coupling capacitor at the input, in the middle, at the output or as a power supply capacitor or before the transformer or anywhere else. The same goes for diodes and resistors and coils... and tube or transistor or whatever. This information goes beyond the usual training at universities and institutes.
The majority of circuits in analog audio SEPARATE the half-waves of ONE signal (consisting of two half waves: "positive" and "negative") and amplify it separately (push pull). With the knowledge of the audible difference of even the same parts...: it should be self-explanatory about the suitability of circuit concepts for different applications such as motor or audio amplifier...-) This information goes beyond the usual training at universities and institutes.
Many of these circuits are also half-wave NON-symmetrical: the half-waves also run through two various complex amplifiers: positive and negative amplifiers are not identical, not mirrored. Which gives an audio signal... self-explanatory;-) This information also goes beyond the usual training at universities and institutes.
Like this;-?
Most audio circuits end up as signal loops (feedback) - a simple front in - back out cannot be defined. These correction, control loops serve to suppress swing (electrical circuits are also swing systems, comparable to mechanical ones such as piano strings and piano)
Aside:
The sonic influence of components does not only occur as part of the idealized signal path. A capacitor with, for example, a "delicate and colorful sound character" influences the sound of a device at any point to the same extent, whether as a coupling capacitor at the input, in the middle, at the output or as a power supply capacitor or before the transformer or anywhere else. The same goes for diodes and resistors and coils... and tube or transistor or whatever. This information goes beyond the usual training at universities and institutes.
The majority of circuits in analog audio SEPARATE the half-waves of ONE signal (consisting of two half waves: "positive" and "negative") and amplify it separately (push pull). With the knowledge of the audible difference of even the same parts...: it should be self-explanatory about the suitability of circuit concepts for different applications such as motor or audio amplifier...-) This information goes beyond the usual training at universities and institutes.
Many of these circuits are also half-wave NON-symmetrical: the half-waves also run through two various complex amplifiers: positive and negative amplifiers are not identical, not mirrored. Which gives an audio signal... self-explanatory;-) This information also goes beyond the usual training at universities and institutes.
Like this;-?
Although the first post was 10 years ago, it is a valid question.
Most (commercial) amplifiers (and integrated circuits) are 'loop amplifers', relying on the negative feedback correction to flatten out all errors.
So 'tracing a signal path in an amplifier schematic' is like poking within the loop, most often with capacitive probes and antenna alike wires and other nasty things. It is only at the last voltage gain stage (the "VAS") where the signal reappears as if from nowhere. That is of cause because the correction signal is 'masked' by the feedback factor (At = Ao / Au). So within the loop, the signal is hardly tracable.
Say the fixed overall gain is 20dB (10x) and the open loop gain is 100dB (100.000x, not uncommon in opamps), the feedback 'supression is 80db (10.000x).
After the input differential stage, the input signal of say 150mV is 10.000x lower, a mere 15μV. That is actually the very error signal itself... if you want to measure it, your measuring action is now part of the error and spoiling the measurement as a result. The position and velocity of any particle cannot be determined together. That seems to be a fundamental law...
Exempts: open loop amp's, also noted the 'switching gear devices' as in #13 & #12 too. Better have no such switching audio gear at your ears.
Electronics are fun, but there seems no non-switching high power alternatives save the global warming class A classics.
Or... the ultimate act of balancing?
Most (commercial) amplifiers (and integrated circuits) are 'loop amplifers', relying on the negative feedback correction to flatten out all errors.
So 'tracing a signal path in an amplifier schematic' is like poking within the loop, most often with capacitive probes and antenna alike wires and other nasty things. It is only at the last voltage gain stage (the "VAS") where the signal reappears as if from nowhere. That is of cause because the correction signal is 'masked' by the feedback factor (At = Ao / Au). So within the loop, the signal is hardly tracable.
Say the fixed overall gain is 20dB (10x) and the open loop gain is 100dB (100.000x, not uncommon in opamps), the feedback 'supression is 80db (10.000x).
After the input differential stage, the input signal of say 150mV is 10.000x lower, a mere 15μV. That is actually the very error signal itself... if you want to measure it, your measuring action is now part of the error and spoiling the measurement as a result. The position and velocity of any particle cannot be determined together. That seems to be a fundamental law...
Exempts: open loop amp's, also noted the 'switching gear devices' as in #13 & #12 too. Better have no such switching audio gear at your ears.
Electronics are fun, but there seems no non-switching high power alternatives save the global warming class A classics.
Or... the ultimate act of balancing?