Hello there , I have a few questions regarding OPAMP and POWER AMP .
I am trying to learn about them. I do not have any background In electronics or electrical engineering I am just a hobbyist and I have a few questions regarding OPAMP and Power Amp .
First Question >
Most Amp Schematic I saw reassembles like Amp 3 , I could not find any amp (power amp or discrete opamp) having circuit diagram of Amp 2 or Amp 1 .
Why Amp 3 model is preferred over two other ways ?
Second Question >
Some AB mode biasing uses a capacitor , while some do not .
What's pro and con of using and not using capacitor in biasing circuit .
Reference schematic Amp 1 and Amp 3
Third Question
While Opamp biases transistors using + or - ve rail .
but power audio amp uses ground to bias transistors.
why ground is used or preferred over + or - ve rail .
what's pro and con of each .
Reference amp 3 and amp 4
I am trying to learn about them. I do not have any background In electronics or electrical engineering I am just a hobbyist and I have a few questions regarding OPAMP and Power Amp .
First Question >
Most Amp Schematic I saw reassembles like Amp 3 , I could not find any amp (power amp or discrete opamp) having circuit diagram of Amp 2 or Amp 1 .
Why Amp 3 model is preferred over two other ways ?
Second Question >
Some AB mode biasing uses a capacitor , while some do not .
What's pro and con of using and not using capacitor in biasing circuit .
Reference schematic Amp 1 and Amp 3
Third Question
While Opamp biases transistors using + or - ve rail .
but power audio amp uses ground to bias transistors.
why ground is used or preferred over + or - ve rail .
what's pro and con of each .
Reference amp 3 and amp 4
Attachments
THe diagrams are all practically the same topologically and in fact differ mostly by various errors in the drawings. Diagram 1 has an error in the bias circuit and would not work. Diagram 2 has no bias for the output. All the diagrams have wrongly ftawn the input protection circuit, which is also completely needlessly drawn as diode connected transistors, which is only done in certain specific circumstances.
Regarding all your other questions, the answers can be found in any book on amplifier design and is almost self-explanatory once you UNDERSTAND (not merely know!) the basic circuits. This is not something you are going to infer from a simulator, because without understanding how the basic circuits making these more complex ones work, you don't even know where to look and what stimulus to set up in a simulator in order to expose problems and virtues of the circuits and compare them.
Regarding all your other questions, the answers can be found in any book on amplifier design and is almost self-explanatory once you UNDERSTAND (not merely know!) the basic circuits. This is not something you are going to infer from a simulator, because without understanding how the basic circuits making these more complex ones work, you don't even know where to look and what stimulus to set up in a simulator in order to expose problems and virtues of the circuits and compare them.
A simulator does not teach understanding.
It allows the knowledgeable to ask questions and see the results/answers quickly.
But long before that one needs to understand how a transistor amplifies and what types of amplifier topology that a single transistor can adopt. Common emitter, common collector, common base. The common collector is also the emitter follower and is more often called this instead.
There are many websites that have transistor tutorials. These can give a good grounding, if you pick the right tutorials.
the .ac are university sites and are more reliable than the many you tube presentations.
It allows the knowledgeable to ask questions and see the results/answers quickly.
But long before that one needs to understand how a transistor amplifies and what types of amplifier topology that a single transistor can adopt. Common emitter, common collector, common base. The common collector is also the emitter follower and is more often called this instead.
There are many websites that have transistor tutorials. These can give a good grounding, if you pick the right tutorials.
the .ac are university sites and are more reliable than the many you tube presentations.
Last edited:
All the designs you show use many more transistors than are really needed.
Just adding more transistors doesnt always result in a large improvement.
Sometimes the improvement is inaudible.
There is also the point that the mopre the components the more is to go wrong and the faults can be more complex.
KISS, keep it simple stupid.
Just adding more transistors doesnt always result in a large improvement.
Sometimes the improvement is inaudible.
There is also the point that the mopre the components the more is to go wrong and the faults can be more complex.
KISS, keep it simple stupid.
true , i am trying to learn , hence simulated design are complex , and from simulation i cannot find the differences , and i have been pointed that schematics are wrong .
Opamps don't have a "ground" rail - the common connections are positive and negative power (rails), non-inverting and inverting inputs, and the output. Basically, there's no real ground to connect a resistor for biasing a constant current source, so it has to connect to the other power rail. The bias resistor dissipates twice the power as it would if connected to a ground halfway between the rails, but even so the current is very low and the power is much less than other devices in the opamp.
An audio power amplifier is basically an opamp with a higher-power output stage used in a non-inverting circuit with two "external" resistors to set voltage gain. There are of course more details, but that's the gist.
Those schematics do have a lot of transistors and can be hard to read and understand all at once. The thread in the link below has a tutorial by Nelson Pass that you might find helpful - he mostly uses field-effect transistors, but he also covers bipolar transistors as most commonly used in analog electronics:
http://www.diyaudio.com/forums/solid-state/51836-nelson-pass-discrete-op-amp.html
- Status
- Not open for further replies.