Does this (textbook) circuit diagram contain a mistake?

In summary: The diagram seems to be correct. The problem is with the placement of the resistor in the circuit.The diagram seems to be correct. The problem is with the placement of the resistor in the circuit.
  • #1
kostoglotov
234
6

Homework Statement


[/B]
This circuit solves some differential equation, the question is asking for the equation based on the circuit diagram

b1npQSK.png


imgur link: http://i.imgur.com/b1npQSK.png

Homework Equations

The Attempt at a Solution



I refer to the input terminal for -f(t)...the signal from it doesn't seem to pass through any resistor on its way into the inverting summer, so I've no way (I think) of finding how the signal from -f(t) is scaled in the summer.

Is this a mistake on the diagram? If not, what am I missing?
 
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  • #2
Could be a current input rather than a voltage input... or a mistake.
 
  • #3
Yes - I am sure, it is a mistake. The right most amplifier must add up three signals (voltages) - and for this purpose another series resistor is necessary.
 
  • #4
LvW said:
The right most amplifier must add up three signals (voltages)...

Where does the problem statement say that? Did you leave something out?
 
  • #5
Tom.G said:
Where does the problem statement say that? Did you leave something out?
It is the purpose of the circuit to "solve differential equations".
Hence, it needs an input. Such an input (time domain) is shown as "-f(t) directly at the inv. terminal of an opamp, which - at the same time - receives the sum of two other voltages. However, this addition works only if f(t) also is connected through another resistor (remember the virtual ground principle).
Thus, without such a resistor the whole circuit makes no sense.
 
  • #6
LvW said:
...this addition works only if f(t) also is connected through another resistor...

That input is acting as a transimpedance amplifier. It is a current input. You can use KCL to help wrap your head around it.
https://en.wikipedia.org/wiki/Transimpedance_amplifier
 
  • #7
Tom.G said:
That input is acting as a transimpedance amplifier. It is a current input. You can use KCL to help wrap your head around it.
https://en.wikipedia.org/wiki/Transimpedance_amplifier
A "current input" is nothing else than a voltage input with a corresponding large source resistance (see my answer).
On the other hand - do you really assume that such a circuit (analog computer circuitry for solving differential equations) is intended to work with current in and voltage out? This would make no sense at all.
 

1. What should I do if I suspect a mistake in the circuit diagram of my textbook?

If you suspect a mistake in the circuit diagram of your textbook, it is important to first double-check your work and make sure you have properly interpreted the diagram. If you still believe there is a mistake, you can reach out to the publisher or author of the textbook for clarification or to report the error.

2. How can I tell if there is a mistake in the circuit diagram?

If you are unsure whether there is a mistake in the circuit diagram, you can compare it to other sources or consult with an experienced electrical engineer. You can also use circuit simulation software to test the diagram and see if it produces the expected results. If there are any inconsistencies or errors, it is likely there is a mistake in the diagram.

3. Can a mistake in the circuit diagram affect my understanding of the concept?

Yes, a mistake in the circuit diagram can definitely affect your understanding of the concept. It may lead to incorrect calculations or assumptions, which can impact your overall understanding of the topic. That is why it is important to verify the accuracy of the circuit diagram before using it for your studies or projects.

4. Who is responsible for ensuring the accuracy of circuit diagrams in textbooks?

The responsibility for ensuring the accuracy of circuit diagrams in textbooks falls on the publisher and author. They are responsible for thoroughly reviewing and fact-checking all the content in the textbook, including the diagrams. However, it is also important for readers to report any errors they may find to help improve the accuracy of future editions.

5. Can I use a circuit diagram from a different source if I believe there is a mistake in my textbook?

Yes, you can use a circuit diagram from a different source if you believe there is a mistake in your textbook. However, make sure to properly cite the source and verify the accuracy of the diagram before using it in your work. It is always best to consult with multiple sources to ensure the correctness of the information.

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