Transformers

Abstract

Within an integrated circuit, active devices such as bipolar and MOS transistors can be realized readily along with certain passive devices such as resistors and capacitors. Inductors and transformers cannot be realized except for high-frequency applications [21], [22]. Although tuned, bandpass frequency responses can be realized with ICs containing feedback amplifiers, resistors and capacitors only, for many moderate-frequency applications, an inductor is needed and an element external to the IC must be utilized. Often, it is almost as convenient to achieve a two-winding ‘coil’ as one-winding; therefore, the transformer is available.