Select a transformer with the correct turns ratio to match the 8- resistive load in Fig. 4.3 to the Thevenin equivalent circuit of the source.
1. Determine the Turns Ratio
The impedance of the input circuit, Zi, is 5000 . This value represents the Thevenin impedance of the source. The load impedance, ZL , is 8 .
To achieve an impedance match, the required turns ratio is
Therefore, the impedance-matching transformer must have a turns ratio of 25:1.
Related Calculations. The maximum power transfer theorem (Sec. 1) states that maximum power is delivered by a source to a load when the impedance of the load is equal to the internal impedance of the source.
Because the load impedance does not always match the source impedance, transformers are used between source and load to ensure matching.
When the load and source impedances are not resistive, maximum power is delivered to the load when the load impedance is the complex conjugate of the source impedance.