High value resistors (electronics)

High value resistors (HVR) are electronic components used for special applications, such as in bio-medical systems, measurement equipment and some condenser microphones. While discrete resistors in the range of few tens of megohm are very common, making giga-ohm range resistors is more complicated. Discrete resistors are available up to several tera-ohms, but are expensive because of limited demand. Sometimes, a combination of active and passive electronic devices is used to achieve such a high resistance.<ref>A. Tajalli, et al., "Implementing ultra-high-value floating tunable CMOS resistors," IEE Electronic Letters 2008</ref>