# Confused on Voltage Calculations: Using Nodal Analysis to Find Input to Amp

• righteous818
In summary, the conversation discusses calculating the voltage through the auxiliary circuit and using nodal analysis to find the voltage input to the amplifier. It is mentioned that the voltage entering the circuit has a maximum of 10V and the amplifier has an infinite impedance. The gain is determined to be 6 in order to recover the output of the voltage divider. The 0.5A current is not part of the solution but is the source of the problem. The division ratio and current are used to find the resistors that give the desired voltage ratio, but the resistance may change if the auxiliary circuit is placed over the resistor. The goal is to have 10V across the resistor so the amplifier can amplify it back to 10V.
righteous818
I have attachted the question as a picture:

my first attempt i calculated the voltage through the auxillary circuit to be 10V but i am confused of where the 0.5 A plays in this part, then i used nodal analysis to find the voltage input to the amplifier but up to that point i am confused of how to proceed, am i working the question through the right steps or am i missing something

I think the voltage entering the circuit has a maximum of 10V from the voltage divider.

When I carry out the nodal analysis I get 1/3 of the starting voltage at the first node, and 1/6 of the starting voltage at the 2nd node ... and since the amplifier has "infinite impedance" it will see this 1/6 value.

Thus the gain must be 6 in order to recover the output of the voltage divider.

Clearly the 0.5A current is routed not through the amplifier, but down and around the return loop (implied ground). So the 0.5A is not part of the solution, but the source of the problem!

what i did is used the division ratio an the current and the high voltage to find 2 resistors that will give that division ratio but remember if u put the auxillary circuit over the resistor which gives that 10V it will change the resistance thus i found the the new voltage across it then found the voltage at the node going intot the amplifier, so remember what we want is 10 v across that resistor so the amplifier has to amplfiier it back to 10v, that's what i did

## 1. What is nodal analysis and how is it used to find input to amps?

Nodal analysis is a method used to analyze electrical circuits by finding the voltage at each node or intersection between components. It is based on Kirchhoff's Current Law, which states that the sum of currents entering a node must equal the sum of currents leaving the node. By applying this law, we can create a system of equations to solve for the unknown voltages at each node, including the input to amps.

## 2. What is the difference between nodal analysis and other circuit analysis techniques?

Nodal analysis is different from other techniques such as mesh analysis or Thevenin's theorem because it is based on the voltage at each node rather than the current through each component. This can be useful when dealing with complex circuits with multiple voltage sources or when trying to find the input to amps in a circuit.

## 3. How do I set up a nodal analysis problem to find the input to amps?

To set up a nodal analysis problem, you will need to identify all the nodes in the circuit and label them with a voltage variable. Then, use Kirchhoff's Current Law to create equations for each node, including the unknown input to amps. You can then solve the system of equations to find the input voltage.

## 4. Can nodal analysis be used for both AC and DC circuits?

Yes, nodal analysis can be used for both AC and DC circuits. However, for AC circuits, the voltage at each node will be represented by a complex number rather than a simple numerical value. This means that the equations will need to be solved using complex algebra.

## 5. Are there any limitations to using nodal analysis to find the input to amps?

While nodal analysis is a powerful tool for analyzing circuits, it does have some limitations. It can become more complex and time-consuming for circuits with a large number of nodes or when dealing with non-linear components. In these cases, other analysis techniques may be more efficient.

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