Super capacity

Circuit for realizing a super-capacitor D . Right the switch symbol

A supercapacitance is an elementary electronic circuit which is a form of impedance converter . The application is in the area of analog low-pass filters . The circuit was presented in 1969 by LT Bruton as part of the Bruton transformation (FDNR technique). In this transformation, frequency- independent ohmic resistances become linear frequency-dependent capacitors and capacitors become supercapacitors whose purely real impedance depends on the square of the frequency .

The circuit consists of two operational amplifiers , two capacitors and three ohmic resistors that determine the specific value of the supercapacitance. For a simplified representation, a special symbol with the designation D is usually used in circuit diagrams , as shown in the adjacent figure.

The value of the real impedance at connections 1 and 2 of a supercapacitor is:

${\displaystyle Z_{D}={\frac {-1}{\omega ^{2}\cdot D}}}$

with the value and dimension for D , which is determined by the passive components of the circuit as:

${\displaystyle D=R_{1}\cdot C_{1}\cdot C_{2}}$

${\displaystyle D=\left[{\frac {As^{2}}{V}}\right]}$

The two resistors with the designation R have no influence on the value of D , but they must have the same values. In practical filter circuits, all three resistors are usually chosen with the same value.

literature

• Lutz v. Wangenheim: Active Filters and Oscillators . 1st edition. Springer, 2008, ISBN 978-3-540-71737-9 .

Web links

• G. Krucker : Active filters based on LC structures (PDF; 162KiB) March 23, 2003. Retrieved February 18, 2011.

Individual evidence

1. ^ LT Bruton: Network Transfer Functions Using the Concept of Frequency Dependent Negative Resistors , IEEE, Circuit Theory, 1969, issue CT-16, pages 406 to 408