# Constraint on Thevenin impedance

• PatrickCummin
In summary: This has been proven using linear algebra and impedance matrices. Additionally, the concepts of driving-point impedance and Thevenin/Norton reduction can also be understood in the context of an impedance matrix with I and V vectors.
PatrickCummin
Let's say we have a circuit composed of simple linear circuit elements (resistors, inductors and capacitors). Now we calculate the Thevenin equivalent circuit for some load within this circuit, and we determine the Thevenin impedance, Z_t.

My question is this: Is it generally the case that the real part of Z_t is positive (Re Z_t greater than or equal to zero)? In particular, has this been proven to be generally the case?

Thanks for any help, Patrick

PatrickCummin said:
Let's say we have a circuit composed of simple linear circuit elements (resistors, inductors and capacitors). Now we calculate the Thevenin equivalent circuit for some load within this circuit, and we determine the Thevenin impedance, Z_t.

My question is this: Is it generally the case that the real part of Z_t is positive (Re Z_t greater than or equal to zero)? In particular, has this been proven to be generally the case?

Thanks for any help, Patrick

Hi Patrick. The simple answer is that for linear circuits containing only independent sources then yes the real part of the Thevenin impedance is non-negative. However for circuits containing dependent sources the Thevenin resistance may be negative.

Last edited:

## 1. What is the Thevenin impedance?

The Thevenin impedance is a simplified representation of a complex electrical network. It is the equivalent impedance of a circuit when viewed from two designated points, known as the Thevenin terminals.

## 2. Why is it important to consider constraints on Thevenin impedance?

Constraints on Thevenin impedance help ensure that a circuit will function properly and efficiently. They take into account factors such as maximum power transfer and stability.

## 3. How do you calculate the Thevenin impedance?

The Thevenin impedance can be calculated by disconnecting all sources in the circuit and determining the equivalent impedance between the designated Thevenin terminals. This can be done using various techniques such as voltage division or mesh analysis.

## 4. What are some common constraints on Thevenin impedance?

Some common constraints on Thevenin impedance include maximum power transfer, minimum and maximum voltage and current values, and stability requirements.

## 5. How can constraints on Thevenin impedance be satisfied?

Constraints on Thevenin impedance can be satisfied by designing the circuit with the specified constraints in mind, using appropriate components and techniques. Testing and simulation can also help ensure that the constraints are met in the final circuit.

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