Impedance Matching Calculator

Impedance matching

Impedance Matching Formula

Impedance matching formula

Enter any 3 values to compute the 4th value. 3 form fields must be entered.


This impedance matching calculator can calculate the impedance of the primary or secondary circuit so that the necessary impedance value can be determined for optimum performance of a circuit.

In electronics, there are many instances where circuits require a specific load impedance for optimum performance. The impedance of the load dissipating power may differ drastically from the impedance of the source of the circuit. In other words, the source is the primary circuit, while the load is the secondary circuit. In the case where the impedance of the source and load differ greatly, a transformer can be used to change the actual load into an impedance of desired value. This is referred to as impedance matching.

The factors which affect impedance matching are the turns of the primary circuit, the turns of the secondary circuit, the impedance of the primary circuit, and the impedance of the secondary circuit.

The turns is the amount of times wire is wrapped around the primary and secondary circuit. The turns ratio, the ratio of the primary to secondary turns, is a crucial factor affecting impedance matching. If the turns ratio is greater than 1, then the primary circuit has more turns than the secondary. If less than 1, the secondary circuit has more turns than the primary.

The impedance is the second factor affecting impedance matching. The impedance is the amount of resistance that each circuit, primary and secondary, offer. This is measured in unit ohms (Ω).

To use this calculator, a user just enters any 3 values to compute the 4th value. 3 form fields must be entered in for this calculator to compute the 4th unknown value. Any value of out the 4 variables can be computed, as long as the other 3 values are entered.

Example Calculation

Calculate the primary impedance, ZP, of a transformer circuit if the transformer has a primary circuit with 500 turns and a secondary circuit with 1000 turns. The secondary circuit has a 2000Ω load impedance attached to it.

The known values are:

Primary turns, NP: 500
Secondary turns, NS: 1000
Secondary impedance, ZS: 2000Ω

Solving for ZP:

ZP= ZS x (Turns Ratio)2=
2000Ω (500 turns/1000 turns)2= 2000Ω(0.5)2= 500Ω

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