Presidio’s patented thick film technology buries
electrodes into the ceramic body (Fig. 1) allowing a 10:1 advantage over a conventional construction (Fig. 2). It offers the designer: (a) more bandwidth through increased device capacitance, (b) more stable capacitance over temperature and (c) more
capacitance in smaller case sizes for increased board density.
Filled vias connect the buried electrodes with the outside top and bottom metallization pads; 99.95% pure Au is standard for all metal connections allowing proven wire bond techniques with AuSn or conductive epoxy die attach techniques.
Excellent low loss performance for high Q applications as demonstrated with a 10 pF
NPO capacitor shown in Fig. 6 below.
Ease of dielectric material selection: Presidio offers 3 ceramic materials while
most other suppliers offer more than 15.
Using the KENT SIMULATOR (Fig. 3), a designer can obtain commonly needed RF capacitor parameters in graphical format for popular Presidio Components RF capacitors. In addition, S-parameters for selected capacitors can be saved in S2P format. All device parameters are derived from a series transmission line model developed by Dr. Gordon Kent and available at www.presidiocomponents.com. A technical discussion of the simulation used in the Kent Simulator is presented by Gordon Kent in the “Summary of the Capacitor Simulator.”
Fig. 3. Kent Simulator Version 2.0
A filter design requires a specific capacitance value, CF, and at the upper end of the filter response, fF, the effective capacity must not exceed CF by more than a specified amount of ΔC. Once CF is determined, case size, voltage rating and temperature characteristics can be selected. Typically, lower loss Class I materials like NPQ and NPO are first choice. See Fig. 4.
Fig. 4. Modeled ESR/50 and Ceff of part
Class II “BX” dielectric is typical for DC block or RF bypass applications to operate resonance free over a specified broad frequency range. Low impedance is typically more important than the capacitance value which should be large enough to cover the 3 dB low edge of the bandwidth. See Fig. 5.
Fig. 5. Modeled S21 and Z/50 of part
LSA1010B101MGH5C–, Class II Dielectric
MINIMUM LOSS, FINITE BAND COUPLING CAPACITOR
When minimum loss is required, e.g. a low noise circuit, a high Q capacitor with Class I dielectric (NPQ or NPO) is recommended. Any parallel resonance frequency of the capacitor should be outside of the use frequency band. The best capacitor choice puts the series resonance at the band center (approximately f0 / 2). See Fig. 6.
Fig. 6. Modeled S21 and Ceff of part
NSA3030N100J2H5C–, Class 1 Dielectric
Presidio Components, Inc., has been an industry leader in the manufacture of ceramic capacitors since 1980. We provide high quality commercial capacitors, military capacitors, space capacitors, high temperature capacitors, pulse energy capacitors for EFI detonators, microwave capacitors and RF capacitors, as well as custom capacitors. Our custom products include nonstandard part sizes and voltages, including high voltage, high temperature, high "Q", custom leads, cryogenic ceramics, negative and positive temperature characteristic ceramics and piezoelectric formulations. We have a series of patented microwave and radio frequency products including patented single layer and broadband DC blocking caps. Call Presidio at (858) 578-9390.