Book chapter, 2018
© 2008 by Taylor & Francis Group, LLC. All rights reserved. A varactor is a nonlinear reactive device used for harmonic generation, parametric amplification, mixing, detection, and voltage-variable tuning . However, present applications of varactors are mostly harmonic generation at millimeter and submillimeter wave frequencies and as tuning elements in various RF & microwave applications. Varactors normally exhibit a voltage dependent capacitance and can be fabricated from a variety of semiconductor materials . A common varactor is the reverse-biased Schottky diode. Advantages of varactors are low loss and low noise. The maximum frequency of operation is mainly limited by a parasitic series resistance; see Figure 13.1.