repeating coil
Technically, a transformer corresponds to a transformer in which two closely coupled magnetic fields induce the alternating voltage of the primary coil into the secondary coil. In terms of application, transformers are used for the power and voltage conversion of low frequencies such as the mains frequency or audio frequencies.
Transformers are primarily used for galvanic isolation between two circuit units and are used in high-frequency technology. They can separate high-frequency useful signals from low-frequency interference signals and suppress asymmetrical signals.
Since there is a parasitic coupling capacitance between the primary and secondary windings, the common- mode rejection depends directly on it and is higher the lower the coupling capacitance. The leakage inductance is also included in the common-mode rejection. This is lower the stronger the magnetic flux is guided in the ferrite core.
RF transformers are used, among other things, for balancing RF signals. Thus, when an asymmetrical signal needs to be transformed into a symmetrical signal. This can be done, for example, when feeding balanced antennas with unbalanced cables, or in baluns in which impedance and symmetry matching of different transmission media is performed. Corresponding RF or broadband transformersare used for balancing. They have a toroidal core or rod core and unbalanced turns on the primary side and balanced turns on the secondary side with a center tap.