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Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Dispositivos Semiconductores
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Capacitores
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Modelo idealdv
i CdtA
C kd
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Electrical Parameters (V)
Rated Voltage (UR) Direct voltage for which the C has been
designed Operating Voltage (UOP)
Range (between 0V and Ur) typ. 60% Surge Voltage (US)
For short periods of time Superimposed AC, ripple voltage Reverse voltage
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Electrical Parameters (C)
AC/DC capacitance
AC value is measured at 20oC / 100Hz-120Hz Rated capacitance
Nominal value Tolerance
Described by a code
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Electrical Parameters (C)
Temperature dependence
Frequency dependence
Charge-discharge proof Frequent
charging/discharging cycles may lead to capacitance variation
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Electrical Parameters (tan δ)
Dissipation factor tan δ
R
1/ j C tan R C
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Electrical Parameters (tan δ)
Tan δ variation with temperature and frequency
As freq. increases the capacitive impedance reduces and the dissipation factor gets worse
Increasing the temperature results in better dissipation factor
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Electrical parameters (Z)
R = dielectric losses, series resistance
L = winding and terminals (only depends on f )
C and R depend on temp. and f
Fig. Temperature behaviour is for an Al electrolytic capacitor
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Electrical Parameters (I) Leakage current: depends on time, temperature
and applied voltage
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Electrical Parameters (I)
Ripple current: rms value of circulating current
Depends on temp. and frequency Useful life: life achieve without
exceeding a specified failure rate. Depends on: Temperature Ripple current Voltage
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Electrical Parameters (I)
Useful life: Calculation
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Climatic conditions
UCT: Upper category temperature LCT: Lower category temperature Limits within cap. Can be continuously
operated Storage temperature
There are also restrictions on mechanical stress
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Capacitor Types
Electrolíticos Al Ta
Cerámicos G1 G2
Film Polietileno (polyester) Polipropileno Metalizados
Mica
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Capacitor Types: Values
Electrolíticos Al Ta
Cerámicos G1 G2
Film Polietileno (polyester) Polipropileno Metalizados
Mica
0.47µF-10.000µF / 5V-500V 220nF-100µF / 1V – 50V
0.5pF – 560pF / 63V – 500V 100pF – 470nF / 53V – 500V
1nF - 1µF / 100V – 1000V
10nF - 10µF / 63V – 1000V
2pF – 22nF / 250V – 4000V
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Capacitor Types: Tolerances
Electrolíticos Al Ta
Cerámicos G1 G2
Film Polietileno (polyester) Polipropileno Metalizados
Mica
-10% / +100 % +- 20%
2%, 5%, 10% +- 20%
2%, 5%, 10%
0.5% - 20%
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
AL Electrolytic
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Electrolytic (Al) Capacitors
Polar elements. Only block current in one direction
Anode is Al of great purity. Cathode is electrolyte (liquid) and paper
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Electrolytic (Al) Capacitors
Anode is etched to provide more surface
Dielectric is obtained by oxidation of Al (<1um thickness)
Big values of capacitance
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
V-I curve
After the forming voltage (Uf) current increases
Safe operation is ensured below Ur
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Temperature effects
With decreasing temperature, the viscosity of the electrolyte increases, thus reducing its conductivity.
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Datasheet
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Tantalium-Niobium Caps.
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Electrolytic (Ta-Nb) Capacitors εr is 27 for Ta, 41 for Nb Polar elements. Only
block current in one direction
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Frequency dependence
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Z and ESR
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Low ESR series
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Ultra-low ESR
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Maximum V,I vs T and I vs. f
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Dissipation factor (vs. f, T)
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Leakage
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Ceramic
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Ceramic capacitors
they all have the oxide ceramic dielectric in common.
Ceramic generally means that an inorganic polycrystalline body is formed by sintering at high temperatures.
By means of special production methods, extremely thin layers of ceramic materials can be obtained.
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Classification
Class 1 capacitors The dielectric (200) primarily consists of a
mixture of metal oxides and titanates. Defined linear temperature coefficient with
reversible temperature dependence Capacitance does not vary with voltage. Low losses at frequencies up to the UHF range High insulation resistance Applications: resonant circuits, filters, timing
elements
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Classification Class 2 capacitors
The dielectric ( 200 to 10000) primarily consists of titanates (barium, calcium, strontium) and zirconates.
Non-linear dependence of capacitance on temperature and voltage
Somewhat higher losses and lower insulation resistance than class 1 capacitors
Capacitance decreases according to a logarithmic function (ageing).
High capacitance values even with small-size capacitors are possible
Applications: coupling, blocking, filtering.
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Class 1: Temperature dependence
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Class 2: Temperature dependence
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Termal characteristics
Change more (class 2) or less (class 1) with temperature.
Change in crystalline structure capacitance value of high K
materials (with a high dielectric constant, e.g. X7R, Z5U) class 2 drastically decreases above the Curie point
materials with a low dielectric constant (C0G) class 1, dissipation factor increases considerably at high temperatures.
high ambient temperature and high electrical energy exchange contributes to heating the capacitor.
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Datasheets (C0G)
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Datasheets (X7R)
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Frequency response
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Film Capacitors
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Classification
T ˆ= Polyethylene terephthalate (PET) P ˆ = Polypropylene (PP) N ˆ= Polyethylene naphthalate (PEN) An M (ˆ = Metallization) is prefixed to the short identification code of capacitors with
metallized films.
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Winding method
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Stacked method
The “master capacitors” are produced under well-defined and constant conditions.
Since each individual layer acts as a separate capacitor element, any damage to the contacts due to overloading is restricted to the respective capacitor element and does not affect the entire capacitor
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Film vs. Foil
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Self-healing property
Capacitors with metallized plastic film have a decisive advantage over capacitors with metal foil electrodes: they have self-healing properties. Self-healing properties permit utilization of full
dielectric strength of dielectric materials of metallized film capacitors
metal-foil electrode capacitors must always be designed with a safety margin to allow for any possible faults in the dielectric.
Metallized types thus have a distinct size advantage, which is particularly apparent with the larger capacitance ratings.
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Self-healing property
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Temperature
Polypropylene capacitors have negative temperature coefficient Polyester capacitors have positive temperature coefficient
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Humidity
the dielectric and the effective air gap between the films will react to changes in the ambient humidity
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Frequency
MKT , MFT and MKN
MKP and MFP capacitors: Up to a frequency of 1 MHz, the capacitance remains virtually unaffected by the frequency.
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Maximum voltage (T)
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
V/I limitations
A) corona discharge B) Thermal
dissipation C) Leads resistance
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Tan δ
Polypropelene capacitors
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Tan δ
The dielectric of MKT capacitors contributes a considerably greater dielectric component tan δD
MKT capacitors display a noticeably higher overall dissipation factor, especially at lower frequencies than MKP and MKN capacitors
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Datasheets
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Polyester
Metallized Polyester Capacitors (Mylar) With tolerance of 10% Temperature range -40oC to +85oC. Non inductive. Dielectric strength of 150% of rated
voltage for less than 5 sec
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Polyester
Metallized Polyester Film Capacitors With tolerance of 10%. Operating temperature -40oC to +85oC. Non Inductive Design Compact Size Available in rolls of 100 or 1,000 at special
prices.
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Mica
Advantages: dielectric material (mica) is inert. Does NOT change physically or chemically with age Good temperature stability. Very resistant to corona damage Unless properly sealed, susceptible to moisture pick-
up (increases the power factor and decrease insulation resistance).
Higher cost (scarcity of high grade dielectric material) and manually-intensive assembly.
Silver mica capacitors have the above mentioned advantages. In addition, they have much reduced moisture infiltration.
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Summary
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Summary Ceramics: low stability and precision. Electrolytic - Same as ceramics except they have much
smaller physical size for a given value. Usually polarized. Large tolerances
Tantalum - Better characteristics than electrolytic but still small for high capacity values. Polarized. Smaller tolerance than electrolytic
Poly film – (polyester or polypropylene) --mostly replaced paper capacitors-- Slightly better characteristics than common ceramics. Usually very low leakage currents.
Mica/Silver Mica - Temperature stable, low dissipation factor. Usually large physically.
Polystyrene, Teflon - Very temperature stable. Polystyrene breaks down, however, at high temps (say >80C)
Glass, Air, Oil – Not Common(HV work, big motors)
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Electrolytic Capacitors Tantalum
Small size Large values Medium inductance Quite high leakage Usually polarized Expensive Poor stability Poor accuracy
Aluminum Large values High currents High voltages Small size High leakage Usually polarized Poor stability Poor accuracy Inductive
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Mica
Widely used in low and medium power RF equipment
Low loss at HF Low inductance Very stable Available in 1% values or better Quite large Low values (<10 nF) Expensive
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Film
Polyester 0.3% to 0.5% Moderate stability Low cost Wide temperature
range Low inductance
(stacked film) Large size High inductance
Polypropylene 0.001% to 0.02% Inexpensive Wide range of values Large case size High inductance
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Appendix
Copyright Pedro Julián. Dispositivos Semiconductores - DIEC/UNS 2008
Surface mount formats capacitors 1. A-case (Tantalum
cap) 2. D-Case (Tantalum
cap) 3-4 Electrolytic cap 5. 0805 Ceramic 6. 1206 Ceramic 7. 1210 Ceramic 8 . High Q Porcelan
RF 9. Variable Trimmer