WO2010031428A1

WO2010031428A1 - Glass panel

Info

Publication number: WO2010031428A1
Application number: PCT/EP2008/062341
Authority: WO
Inventors: Antoine Luijkx; Carmelo Dado; Grégory STEFANA
Original assignee: Agc Flat Glass Europe Sa
Priority date: 2008-09-17
Filing date: 2008-09-17
Publication date: 2010-03-25
Also published as: EP2328750A1; EA201100497A1

Abstract

The invention relates to a glass panel, comprising a first glass substrate (2), comprising an inner surface inside of the panel and an outer surface outside of the panel, and a second glass substrate (4), comprising an inner surface inside of the panel and an outer surface outside of the panel, and at least one inner conductive layer (5), wherein the at least one inner conductive layer (5) is provided on the inner surface of the first glass substrate (2) or on the inner surface of the second glass substrate (4), at least two outer conductive layers (8) are provided on the outer surface of the first glass substrate (2) or on the outer surface of the second glass substrate (4), and the at least two outer conductive layers (8) are electrically separated from each other. The panel of laminated glass (1) according to the invention provides a support friendly way of providing electrical power to the inner conductive layer (5).

Description

GLASS PANEL

The invention relates to a glass panel, comprising a first glass substrate and a second glass substrate. Such a glass panel can be for instance a laminated glass panel or a mul- tiple glazing panel. More particularly, such a glass panel comprises at least one inner conductive layer, wherein the at least one inner conductive layer is provided on the first glass substrate or on the second glass substrate.

Technical Background Laminated glass is a type of safety glass that holds together when shuttered. In the event of breaking, it is held in place by the plastics interlayer, typically of Polyvinylbutyral (PVB), between its two or more layers of glass substrate. The plastics interlayer keeps the layers of glass substrate bonded even when broken, and its high strength prevents the glass substrates from breaking-up into large sharp pieces.

Methods for manufacturing laminated glass are well-known in the window industry since decades. A so-called sandwich of the first glass substrate, the plastics interlayer and the second glass substrate is laminated in an automated laminating line by using the procedure of calendering and autoclaving. Calendering of the glass/plastic laminate means the pre-gluing of the sandwich under the action of a pressure imposed by rolls applied on either side of the glass substrates, optionally with action of heat. The final gluing of the glass substrates by a vacuum/heating cycle, which combines pressure and temperatures, takes place during the step of autoclaving, which completely removes air between the plastics interlayer and the glass substrates. The result is a clear glass lami- nate well known from car windscreens.

In the automotive, aviation and other industries, laminated glass panels with integrated electronic components, such as light emitting diodes (LED), or with heating facilities are known, e. g. for displaying information or for lighting purposes. For these applica- tion areas, the manufacturing of a laminated glass panel with electronic components typically comprises the steps of depositing a conductive layer on the first glass substrate, realization of electronic circuits in the conductive layer and depositing of electronic components on the conductive layer, connected to the electronic circuits. The plastics interlayer is then deposited on the conductive layer. The sandwich is obtained by the application of the second glass substrate on the plastics interlayer, which is then laminated as outlined before. In each of these applications it is necessary to furnish an electric supply to the conducting layer for supplying electrical power to the electronic components or heating facilities.

EP 1 840 449 describes such a panel of laminated glass with two connectors, wherein each connector is adapted to provide electrical power from outside the panel of laminated glass to a plurality of electronic circuits arranged within the panel of laminated glass. The connectors are provided on the conductive layer and each connector comprises a plurality of spaced insulators arranged at intervals along its length so as to provide alternately electrical connections and non-electrical connections, respectively, between a conductive strip of the connector and the conductive layer at selected positions. Thus, it is possible to supply in an independent way several electronic circuits realized in the conductive layer.

In order to assure a good electric contact between the connector and the conductive layer, the connector can be applied directly onto the conductive layer by means of soldering or indirectly by means of silver spray or conductive glue. The silver spray, which is preferably applied with a brush, is provided on the conductive layer prior to placing the connector on the conductive layer. Applying conductive glue follows a similar method. The intimate contact between the connector and the conductive layer can be realized during the procedure of laminating.

However, if a contact problem appears between the connector and the conductive layer during the manufacturing process, e.g. a bad application of the connector or usage of a bad type of connector, or if a contact problem appears during a subsequent usage of the panel of laminated glass, e.g. a local detachment of the connector and the conductive layer due to heat, or an insulation electric loss due to an application of elevated electric fields, it is difficult to simply repair the panel of laminated glass without delamination, i.e. destruction, of the panel of laminated glass.

Such a step or repairing a panel of laminated glass due to a contact problem is often carried out manually, is delicate, is critical and takes a relatively long time compared to the time of manufacturing the panel of laminated glass.

The same issues can occur in the case of a double glazing panel comprising LEDs such as the double glazing windows 1,2 or l',2' of figures Ia and Ib described in WO2008074800A1. Such a window can comprise two glass substrates, one of which being provided with a conductive coating supporting the LEDs, separated by an air gap and assembled thanks to a spacer material. A connector can be soldered to the conductive layer during the manufacture process of the window in order to connect the LEDs of the window to an external power source (to supply electrical power to the LEDs). Thus in case of failure of the connector, it is difficult to simply repair the double glazing panel without disassembling the double glazing panel which generally damages the glass panel.

Summary of the invention

Accordingly, it is the object of the invention to provide a glass panel with a connector for supplying electrical power to the glass panel, wherein the connector is easy to replace in case a contact problem appears between the connector and a conductive layer of the glass panel.

This object is addressed by a glass panel, comprising a first glass substrate, comprising an inner surface inside of the panel and an outer surface outside of the panel, and a second glass substrate, comprising an inner surface inside of the panel and an outer surface outside of the panel , and at least one inner conductive layer, wherein the at least one inner conductive layer is provided on the inner surface of the first glass substrate or on the inner surface of the second glass substrate, at least two outer conductive layers are provided on the outer surface of the first glass substrate or on the outer surface of the second glass substrate, and the at least two outer conductive layers are electrically separated from each other..

Accordingly, it is an essential idea of the invention to provide at least two outer conductive layers on the outer surface of the first glass substrate or on the outer surface of the second glass substrate. In this way, electrical power can be supplied to the at least two outer conductive layers, which each form a capacitor with an inner conductive layer and thus are adapted for providing electrical power to the at least one inner conductive layer. This is advantageous over the prior art, as electrical power is supplied to the glass panel on at least one outer surface of the glass substrates, i.e. from an exterior of the panel of laminated glass, and not directly to the at least one inner conductive layer by means known from the prior art. This means further that a contact problem with the at least two outer conductive layers providing electrical power to the glass panel can be easily resolved, given that the glass panel does not need to be disassembled (or delaminated in case of a laminated glass panel) and therefore not destroyed anymore. Preferably, the inner conductive layer is provided as a heating facility, such as a windshield, a side pane or an anti-fogging mirror of a car or of a train, a glass window with a transmissive value that can be varied or an electroluminescent layer.

According to another preferred embodiment of the invention, the glass panel comprises at least two inner conductive layers and at least one electric component, wherein the at least one electric component is electrically connected to one inner conductive layer and to another inner conductive layer, and wherein the at least two inner conductive layers are electrically separated from each other. It is further preferred that the electric component is provided as a light emitting diode (LED) or as any other electronic component known from the prior art. It is further preferred that a plurality of electric components are provided, wherein the plurality of electric components are either electrically connected in parallel or in series by means of a plurality of inner conductive layers, and wherein the electric components are preferably electrically connected to the inner conductive layers by means of gluing and/or soldering.

According to another preferred embodiment of the invention, an inner conductive layer is at least partly congruent with an outer conductive layer. As stated above, an inner conductive layer forms preferably a capacitor with an outer conductive layer, which means that as the capacitance of a capacitor depends on the plate size of the capacitor, an inner conductive layer being at least partly congruent with an outer conductive layer influences the capacitance being formed by the inner conductive layer and the outer conductive layer. In general, electrical power can be applied in different ways to the glass panel. However, according to another preferred embodiment of the invention, the glass panel comprises a connector, wherein the connector is electrically connected to an outer conductive layer. It is especially preferred that the glass panel comprises two connectors for supplying electrical power to the glass panel. This is advantageous over the prior art, as such a connector of the glass panel according to the invention can be easily replaced in case a malfunction of the connector electrically connecting to the outer conductive layer occurs during the time of manufacturing or during the time of using the glass panel. In this way, it is not necessary any more to disassemble or delaminate the glass panel for repairing a defect related to the connector electrically connecting the outer conductive layer. Thus, any further defects caused by disassembling or delamination, such as bubbles left between the glass substrates, the inner conductive layer and/or the plastics in- terlayer can be avoided. It is further preferred that the connector is electrically connected to the outer conductive layer by means of gluing and/or soldering.

According to another preferred embodiment of the invention, the glass panel comprises at least three outer conductive layers, wherein at least one outer conductive layer is provided between the at least two outer conductive layers that are each electrically connected to a connector. In other words, it is preferred that at least one outer conductive layer is provided in between the at least two outer conductive layers that can be supplied with electrical power via the connectors. Thus the at least one outer conductive layer arranged in between the at least two outer conductive layers forms an electrical insulation between the at least two outer conductive layers that can be supplied with electrical power via the connectors.

In general, the glass panel can be supplied with electrical power by a power supply. However, according to another embodiment of the invention it is preferred that the glass panel comprises a power supply and an inductance, wherein the power supply and the inductance are electrically connected in series, and wherein the power supply and the inductance electrically connected in series are adapted for providing electric power to the glass panel via the at least two connectors. According to another preferred embodiment of the invention, the inductance is dimensioned in relation to a capacitive element formed by an inner conductive layer and an outer conductive layer and a resistance formed by the electric component and/or the inner conductive layer for diminishing an overall circuit impedance. As a matter of fact, it is possible to compensate the capacity formed by the inner conductive layer and the outer conductive layer for diminishing an overall circuit impedance of the circuit formed by the power supply, the inductance, a first capacitor being formed by an outer conductive layer and an inner conductive layer, a resistance of the electronic component and/or an inner conductive layer, and a second capacitor formed by an inner conductive layer and an outer conductive layer. In other words, this RLC circuit can be optimized by using the inductance and well adapted frequencies for compensating the capacity and to diminish the circuit impedance. According to another preferred embodiment of the invention, the inner conductive layer and/or the outer conductive layer comprises an underlying coating comprising a conductive oxide such as silicon oxide carbide and an overlying coating comprising a conductive metal oxide such as SnO₂IF. It is further preferred that the inner conductive layer and/or the outer conductive layer comprises a substantially color neutral coating stack, e.g. a chemical vapor deposition (CVD) coating stack comprising a silicon oxide carbide undercoat and an overlying SnO₂:F coating, wherein the coating has preferably a resistance of about 15 ohms per square.

According to another preferred embodiment of the invention, the panel is a panel of laminated glass and the two glass substrates are laminated together via a plastic inter- layer.

According to another preferred embodiment of the invention, the panel is a double glazing panel, the two glass substrates separated by an air gap being assembled thanks to at least a spacer.

The object of the invention is further addressed by a method for manufacturing a panel of laminated glass, comprising the steps of providing a first glass substrate and a second glass substrate, applying at least one inner conductive layer on the first glass substrate or on the second glass substrate, laminating the first glass substrate and the second glass substrate via a plastics interlayer, and providing at least two outer conductive layers on the second glass substrate, wherein the plastics interlayer is provided on the at least one inner conductive layer, the at least two outer conductive layers are provided on the side of the second glass substrate that faces away from the plasties interlayer, and the at least two outer conductive layers are electrically separated from each other.

The method for manufacturing a panel of laminated glass according to the invention is advantageous, since it allows a provision of electrical power to the inner conductive layer by means of a capacitor formed by the inner conductive layer and the outer conductive layer.

According to another preferred embodiment of the invention, the method for manufac- turing a panel of laminated glass further comprises the step of applying at least one electric component, wherein the at last one electric component is electrically connected to one inner conductive layer and to another inner conductive layer, and wherein the one inner conductive layer and the another inner conductive layer are electrically separated from each other. The electric component can be provided for example as a light emitting diode (LED) or as any other electronic component known from the prior art. In this way it is possible to supply the electric component with electrical power by the capacitors formed by the one inner conductive layer and by the one outer conductive layer and by the another inner conductive layer and by the another outer conductive layer, respectively.

Generally, it is possible to supply electrical power to the panel of laminated glass in different ways. However, according to another preferred embodiment of the invention, the method for manufacturing a panel of laminated glass further comprises the step of applying a connector, wherein the connector is electrically connected to an outer con- ductive layer. Thus, as the connector is electrically connected to the outer conductive layer, it is easily possible to replace a connector due to a malfunction during usage or manufacture, compared to realizations known from the prior art, where the connector is electrically connected to the inner conductive layer.

According to another preferred embodiment of the invention, the method for manufacturing a panel of laminated glass further comprises the step of providing a power supply and an inductance, electrically connecting the power supply and the inductance in series and electrically connecting the power and the inductance electrically connected in series to the connector. Such an embodiment allows an easy provision of electric power to a panel of laminated glass via the connector.

According to another preferred embodiment of the invention, the method for manufac- taring the panel of laminated glass further comprises the step of dimensioning the inductance in relation to a capacity formed by an inner conductive layer and an outer conductive layer and a resistance formed by the electric component and/or the inner conductive layer for diminishing an overall circuit impedance. In other words, and as an example, the circuit formed by the power supply, the inductance, a first capacitor formed by one outer conductive layer and one inner conductive layer, the resistance formed by the electric component and/or the inner conductive layer and a second capacitor formed by another inner conductive layer and another outer conductive layer is preferably optimized by using the inductance and well adapted frequencies to possibly compensate the capacities for diminishing the overall circuit impedance.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

Brief Description of the Drawings In the drawings:

Fig. 1 schematically shows a panel of laminated glass according to a preferred embodiment of the invention in a perspective side view, and

Fig. 2 shows an equivalent circuit diagram of the panel of laminated glass according to the preferred embodiment of the invention.

Detailed Description of the illustrative embodiments

The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Where the term "comprising" is used in the present description and claims, it does not exclude other elements or steps. Where an indefinite or definite article is used when referring to a singular noun e.g. "a" or "an", "the", this includes a plural of that noun unless something else is specifically stated.

Furthermore, the terms first, second and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same em- bodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodi- ments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

As can be seen from Fig. 1, according to a preferred embodiment of the invention, the panel of laminated glass 1 comprises a first glass plate or substrate 2, a plastics inter- layer 3 and a second glass plate or substrate 4, wherein the plastics interlayer 3 is provided between the first glass substrate 2 and the second glass substrate 4. The plastics interlayer 3 may comprise Polyvinylbutyral, for example having the reference Solutia RB41.

As can be seen further from Fig. 1, two inner conductive layers 5 are provided on the first glass substrate 2 on the side of the first glass substrate 2 that faces towards the plastics interlayer 3. An interruption 6 electrically insulates the two inner conductive layers 5. An electric component 7, such as a light emitting diode (LED), is provided on the two inner conductive layers 5 so that the electric component 7 is electrically connected to one inner conductive layer 5 and to another inner conductive layer 5.

Three outer conductive layers 8 are provided on the second glass substrate 4 on the side of the second glass substrate 4 that faces away from the plastics interlayer 3. The three outer conductive layers 8 are electrically separated by two interruptions 6. Two connec- tors 9 are provided on the outer conductive layers 8, wherein one connector 9 is provided and electrically connected to the upmost left outer conductive layer 8 and the second connector 9 is provided and electrically connected to the upmost right outer conductive layer 8. In this way, the outer conductive layer 8 provided between the upmost left outer conductive layer 8 and the upmost right outer conductive layer 8 provides an insulation between the latter two outer conductive layers 8.

The inner conductive layer 5 and/or the outer conductive layer 8 can be provided in a substantially color neutral coated stack, e.g. a chemical vapor deposition (CVD) coating stack comprising an SiO_xC_y undercoat and an overlying SnO₂IF coating, wherein the coating has a resistance of about 15 ohms per square. The plastics interlayer 3 preferably comprises a thickness of 1.52 mm, e.g. 0.5 to 2mm. It is further possible, that the plastics interlayer 3 is replaced by a layer of air or a gas such as argon. The interruption 6 can be provided by a laser ablation of about 70 microns wide. As an alternative, the deposition of the inner conductive layers 5 and/or of the outer conductive layers 8 can be done in a partial way, e.g. in a pattern, which eliminates the need for laser ablation for creating the interruption 6. The LED can be provided for instance as a packaged LED manufactured by the company Nichia.

Fig. 2 shows an equivalent circuit diagram of the panel of laminated glass 1 according to the preferred embodiment of the invention as depicted in Fig. 1. Basically, the equivalent circuit diagram of the panel of laminated glass 1 is separated into a first part 10 showing an equivalent circuit for a power supply 12 and into a second part 11 show- ing an equivalent circuit for the panel of laminated glass 1.

The first part 10 comprises a power supply 12 connected in series with an inductance 13. The second part 11 comprises a first capacitor 15, a resistance 16, the electric component 7 and a second capacitor 17. A circuit 14 is formed by the power supply 12, the inductance 13, the first capacitor 15, the resistance 16, the electric component 7 and the second capacitor 17. As it can be seen further from Fig. 2, the first part 10 of the equivalent circuit diagram showing the power supply 12 and the second part 11 of the electric circuit diagram showing the panel of laminated glass 1 are connected via the connectors 9.

The first capacitor 15 is formed by the utmost left inner conductive layer 5 and the utmost left outer conductive layer 8, as depicted in Fig. 1. The second capacitor 17 is formed by the utmost right inner conductive layer 5 and the utmost right outer conductive layer 8, as depicted in Fig. 1. The resistance 16 either relates to the electronic com- ponent 7 and/or to a resistance of the inner conductive layer 5.

The circuit 14 as depicted in Fig. 2 can be optimized by using an appropriate inductance 13 and well adapted frequencies to compensate the capacity of the first capacitor 15 and the second capacitor 17 for diminishing the overall circuit 14 impedance. Appropriate methods for optimizing so-called RLC circuits 14 are well known from the prior art.

The invention has been illustrated and described in the case of a panel of laminated glass, nevertheless the invention can also be applied in all kind of glass panel comprising at least two glass substrates, for instance in a double glazing panel. In the case of a double glazing panel according to the invention, the interlayer 3 of figure 1 is replaced with an air gap.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

Other variations to be disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures can- not be used to advantage. Any reference signs in the claims should not be construed as limiting scope.

Claims

1. Glass panel, comprising a first glass substrate (2), comprising an inner surface inside of the panel and an outer surface outside of the panel, and a second glass substrate (4), comprising an inner surface inside of the panel and an outer surface outside of the panel , and at least one inner conductive layer (5), wherein the at least one inner conductive layer (5) is provided on the inner surface of the first glass substrate (2) or on the inner surface of the second glass substrate (4), at least two outer conductive layers (8) are provided on the outer surface of the first glass substrate (2) or on the outer surface of the second glass substrate (4), and the at least two outer conductive layers (8) are electrically separated from each other.

2. Glass panel (1) according to claim 1, comprising at least two inner conductive layers (5) and at least one electric component (7), wherein the at last one electric component (7) is electrically connected to one inner conductive layer (5) and to another inner conductive layer (5), and wherein the at last two inner conductive layers (5) are electrically separated from each other.

3. Glass panel (1) according to claim 1 or 2, wherein an inner conductive layer (5) is at least partly congruent with an outer conductive layer (8).

4. Glass panel (1) according to any of claims 1 to 3, comprising a connector (9), wherein the connector (9) is electrically connected to an outer conductive layer (8).

5. Glass panel (1) according to any of claims 1 to 4, comprising at least three outer conductive layers (8), wherein at least one outer conductive layer (8) is provided between the at least two outer conductive layers (8) that are each electrically connected to a connector (9).

6. Glass panel (1) according to any of claims 1 to 5, comprising a power supply (12) and an inductance (13), wherein the power supply (12) and the inductance (13) are electrically connected in series, and wherein the power supply (12) and the inductance (13) electrically connected in series are adapted for providing electrical power to the panel of laminated glass (1) via the at least two connectors (9).

7. Glass panel according to claim 6, wherein the inductance (13) is dimensioned in relation to a capacitive element formed by an inner conductive layer (5) and an outer conductive layer (8) and a resistance (16) formed by the electric component (7) and/or the inner conductive layer (5) for diminishing an overall circuit (14) impedance.

8. Glass panel (1) according to any of claims 1 to 7, wherein the inner conductive layer (5) and/or the outer conductive layer (8) comprises an underlying coating comprising silicon oxide carbide and an overlying coating comprising SnO₂IF.

9. Glass panel (1) according to any of claims 1 to 8, wherein the panel is a panel of laminated glass and the two glass substrates are laminated together via a plastic inter- layer.

10. Glass panel (1) according to any of claims 1 to 8, wherein the panel is a double glazing panel, the two glass substrates separated by an air gap being assembled thanks to at least a spacer.

11. Method for manufacturing a panel of laminated glass (1), comprising the steps of: providing a first glass substrate (2) and a second glass substrate (4), applying at least one inner conductive layer (5) on the first glass substrate (2) or on the second glass substrate (4), laminating the first glass substrate (2) and the second glass substrate (4) via a plastics interlayer (3), and providing at least two outer conductive layers (8) on the second glass substrate (4), wherein the plastics interlayer (3) is provided on the at least one inner conductive layer

(5), the at least two outer conductive layers (8) are provided on the side of the second glass substrate (4) that faces away from the plastics interlayer (3), and the at least two outer conductive layers (8) are electrically separated from each other.

12. Method according to claim 11, further comprising the step of applying at least one electric component (7), wherein the at last one electric component (7) is electrically connected to one inner conductive layer (5) and to another inner conductive layer (5), and wherein the one inner conductive layer (5) and the another inner conductive layer (5) are electrically separated from each other.

13. Method according to claim 11 or 12, further comprising the step of applying a connector (9), wherein the connector (9) is electrically connected to an outer conductive layer (8).

14. Method according to any of claims 11 to 13, further comprising the step of providing a power supply (12) and an inductance (13), electrically connecting the power supply (12) and the inductance (13) in series and electrically connecting the power supply (12) and the inductance (13) electrically connected in series to the at least two connectors (9).

15. Method according to claim 14 , further comprising the step of dimensioning the inductance (13) in relation to a capacitive element formed by an inner conductive layer (5) and an outer conductive layer (8) and a resistance (16) formed by the electric component (7) and/or the inner conductive layer (5) for diminishing an overall circuit (14) impedance.