So, what is the voltage at the inverting input of the second opamp? Is it the same as the non-inverting input of the second opamp, or of the third?

I think I got second stage wrong.

 

I already knew what was said there, and that is still not what I'm asking for, so why are you posting useless links?

Keep in mind that we seldom have a real clear picture of what you do and don't know, particularly regarding fine details. Sometimes a link to or a discussion of the basics fills in a gap that solves the problem. Sometimes it doesn't. When asking strangers for help, you're just going to have to accept that different strangers will provide different help based on what they think might move you in the right direction. Sometimes they'll be right on target, and other times they'll make a clean miss.

 

For every circuit posted there is missing some details:

1) As LvW said : common GND and 0 V.
2) The last stage works as Schmitt Trigger.
3) Power supply for the whole circuit.
4) Signal input source and frequency.
5) Application purpose.

The purpose is just to construct a working amplifier chain. Then I'm going to test how the the amplification and phase changes for higher frequencies.

What are you tryng to amplify?
And why you want to measere phase changes?

Did you read deeply the TL071's datasheet first?

 

I already knew what was said there, and that is still not what I'm asking for, so why are you posting useless links?

*Teknolog - if you know what an OTA is and how it works, why don`t you use the corresponding OTA symbol in your drawing?

* Moreover, I completely agree with the above general comments from WBahn.

 

*Teknolog - if you know what an OTA is and how it works, why don`t you use the corresponding OTA symbol in your drawing?

Teknolog needs to clarify a point here.

I've been assuming that all three stages use a voltage-based opamp but that the configuration of the second stage is such that the second stage acts as a transconductance amplifier while the configuration of the third stage is such that the third stage acts as a transimpedance amplifier. In that case, the symbols used for the opamps would all be the same.

 

I've been assuming that all three stages use a voltage-based opamp but that the configuration of the second stage is such that the second stage acts as a transconductance amplifier ......

But how can a voltage-based opamp "act as a transconductance amplifier" ?

 

I didn't say that the voltage-based opamp acts as a transconductance amplifier, I said that the second stage -- i.e., the circuit block that includes the voltage-based opamp plus some components around it -- acts as a transconductance amplifier.

All a transconductance amplifier is is a circuit that takes a voltage between one pair of nodes and produces a current between another pair of nodes, correct?

Consider the classic inverting amplifier configuration. Remove the feedback resistor and make those your output terminals. Place a load resistance (including a short circuit) across the output terminals and apply a voltage to the input resistor, Rin. What do you get? A current in the load that is proportional to the voltage. What's the transconductance of this amplifier? Simple, 1/Rin (or -1/Rin depending on how you have marked the output terminals).

 

Consider the classic inverting amplifier configuration. Remove the feedback resistor and make those your output terminals. Place a load resistance (including a short circuit) across the output terminals and apply a voltage to the input resistor, Rin. What do you get? A current in the load that is proportional to the voltage. What's the transconductance of this amplifier? Simple, 1/Rin (or -1/Rin depending on how you have marked the output terminals).

That´s what you were referring to? (I think, we shouldn`t confuse the OP).
I am sure you will agree that your above description is
a) trivial (i,in=i,out)
b) does not provide a ground referenced current and, thus, cannot be used for the described task (how will you feed the following transresistance stage?) , and
c) for this reason (b) does not meet the commonly used definition of a transconductance amplifier.

Do you agree?

 

I tried a new configuration.
What do you think about this?

 

Teknolog - may be somebody else can answer your question. I cannot.
I remember that you want to use a transconductance amp anywhere in the chain - and several times I have asked you to use the normal OTA symbol.
Otherwise, one cannot see if and at which place you intend to use an OTA.
What I see is the following:
A non-invertimg opamp amplifier in cascade with a unity gain amplifier and a classical inverting gain stage. All made of normal voltage opamps. Is it that what you want?

 

Teknolog - may be somebody else can answer your question. I cannot.
I remember that you want to use a transconductance amp anywhere in the chain - and several times I have asked you to use the normal OTA symbol.
Otherwise, one cannot see if and at which place you intend to use an OTA.
What I see is the following:
A non-invertimg opamp amplifier in cascade with a unity gain amplifier and a classical inverting gain stage. All made of normal voltage opamps. Is it that what you want?

I think WBahn answered this,

All a transconductance amplifier is is a circuit that takes a voltage between one pair of nodes and produces a current between another pair of nodes, correct?

Also from Wikipedia:

Transconductance amplifiers

A transconductance amplifier (gm amplifier) puts out a current proportional to its input voltage. In network analysis, the transconductance amplifier is defined as a voltage controlled current source (VCCS) . It is common to see these amplifiers installed in a cascode configuration, which improves the frequency response.

You seem to be referring to this which is not what I'm using for this circuit.

I hope you understand what I mean now.

 

You seem to be referring to this which is not what I'm using for this circuit.
I hope you understand what I mean now.

No - I don`t.
Do you remember your first posting?
Here is an excerpt:" If I want to cascade a voltage amplifier, a transconductance amplifier and a transresistance amplifier, how should they be connected?"

Now you state "....which is not what Im`using for this circuit" (with reference to a transconductance unit).

It would be very helpful for us to know what your intention is.
You have shown to us several circuit alternatives - some of them able to work and some of them not.
Can you explain in WORDS what you like to do?

 

Did you read the Wikipedia text I quoted? That's the kind of transconductance amplifier I'm using. As you can see it's called "transconductance amplifier". It doesn't matter if you missunderstood what I meant in my first post, that's what I'm using.

It's hard to answer what the intention is, because it wasn't me who decided to create this circuit. As you can see it's posted in the Homework section. In the instructions for this it says that this cascade circuit should be created and with a gain of 11, then we should answer if the circuit manages to keep the gain when the input frequency is 1 kHz, 10 kHz, 100 kHz and 1 MHz and if not where it doesn't manage anymore. We should also say if there's any phase shift between the input and the output signal.

That's as much purpose that I can give because that's all the instructions I have. Do you understand now?

 

Did you read the Wikipedia text I quoted? That's the kind of transconductance amplifier I'm using. As you can see it's called "transconductance amplifier". It doesn't matter if you missunderstood what I meant in my first post, that's what I'm using.

You make me somewhat confused.
OK - I have learned you are using a transconductance amplifier.
ButI didn`t misunderstand your first post because there you have already mentioned such an amplifier.
However, in your last post you told us the opposite: ...which is not what Im`using for this circuit.
That´s the reason for my confusion.
So - for clarification - you should answer the question which circuit you intend NOT to use.
And again my request: In case you post again a circuit diagram, please use the correct symbol for the OTA.