Impedance emulator
First Claim
1. A impedance emulating device, including:
- a voltage divider having a midpoint node at voltage VX;
said voltage divider including at least one impedance having a reactive component;
an OP AMP having one input connected to VX and the other input connected to the output of said OP AMP, whereby said output of said OP AMP is driven to equal VX;
a load impedance connected at one end to said OP AMP output;
said voltage divider and said load impedance having values scaled so that VX replicates the output of an emulated impedance of predetermined reactance and magnitude.
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Accused Products
Abstract
A method and device to emulate impedances includes a pair of impedances connected in series between a supply voltage and ground, the impedances forming a voltage divider having at its midpoint a reference voltage Vx. An OP AMP includes a positive input connected to the Vx node and the negative input connected to the output thereof in a direct feedback loop. The OP AMP output is also connected to a load impedance that is connected either to the supply voltage or ground. The unity gain OP AMP forces the output voltage thereof to follow the input voltage Vx, whereby the output voltage behaves as if it were created by a virtual impedance. By proper choice of components and values, the virtual impedance may comprise a large capacitor, and the remaining impedances may comprise resistance and small capacitance, both of which, together with the OP AMP, are easily integrated in a small die area. A transistor may be interposed between the load impedance and supply or ground to eliminate unacceptably large current flow through the OP AMP. The OP AMP may be provided with a negative gain, and the impedances may be scaled to create a virtual inductor having a predetermined value. Impedance emulator circuits may be combined so that the emulated impedance of one circuit may act as a virtual component in a further emulation circuit, whereby a wide range of component impedances values of may be replicated.
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Citations
25 Claims
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1. A impedance emulating device, including:
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a voltage divider having a midpoint node at voltage VX;
said voltage divider including at least one impedance having a reactive component;
an OP AMP having one input connected to VX and the other input connected to the output of said OP AMP, whereby said output of said OP AMP is driven to equal VX;
a load impedance connected at one end to said OP AMP output;
said voltage divider and said load impedance having values scaled so that VX replicates the output of an emulated impedance of predetermined reactance and magnitude. - View Dependent Claims (2, 3, 4)
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5. A impedance emulating device, including:
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a voltage divider having a midpoint node at voltage VX;
an OP AMP having one input connected to VX and an output connected to the gate of a transistor, the other input of said OP AMP connected to the source/drain circuit of said transistor, whereby said output of said OP AMP is driven to equal VX;
a load impedance connected at one end to said other input of said OP AMP and said source/drain circuit of said transistor, whereby said source/drain circuit provides a current path to said load impedance;
said voltage divider and said load impedance having values scaled so that VX replicates the output of an emulated impedance of predetermined reactance to and magnitude. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13)
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14. A impedance emulating device, including:
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a voltage divider connected between a voltage supply and ground and having a midpoint node at voltage VX;
an amplifier having an input connected to VX and an output Vy;
a load impedance connected between Vy and said voltage supply;
said voltage divider and said load impedance having values scaled so that VY replicates the output of an emulated impedance of predetermined reactance and magnitude. - View Dependent Claims (15)
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16. An impedance emulating device, including:
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a voltage divider having a midpoint node at voltage VX;
an OP AMP having one input connected to VX and the other input connected to the output of said OP AMP, whereby said output of said OP AMP is driven to equal VX;
a load impedance connected at one end to said OP AMP output;
said voltage divider and said load impedance heaving values scaled so that VX replicates the output of an emulated impedance of predetermined reactance and magnitude;
said voltage divider including impedances KZa and KZb connected in series, and said load impedance including an impedance KZa/K−
1, K being a numerical constant.
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17. An impedance emulating device, including:
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a voltage divider having a midpoint node at voltage VX;
an OP AMP having one input connected to VX and the other input connected to the output of said OP AMP, whereby said output of said OP AMP is driven to equal VX;
a load impedance connected at one end to said OP AMP output;
said voltage divider and said load impedance having values scaled so that VX replicates the output of an emulated impedance of predetermined reactance and magnitude;
said voltage divider including impedances KZa and KZb connected in series, and said load impedance including an impedance KZb/K−
1, K being a numerical constant.
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18. An impedance emulating device, including:
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a voltage divider having a midpoint node at voltage VX;
an OP AMP having one input connected to VX and the other input connected to the output of said OP AMP, whereby said output of said OP AMP is driven to equal VX;
a load impedance connected at one end to said OP AMP output;
said voltage divider and said load impedance having values scaled so that VX replicates the output of an emulated impedance of predetermined reactance and magnitude;
said voltage divider including, impedances KZa/K−
1 and KZb/K−
1 connected in series, and said load impedance including an impedance KZa, K being a numerical constant.
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19. An impedance emulating device, including:
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a voltage divider having a midpoint node at voltage VX;
an OP AMP having one input connected to VX and the other input connected to the output of said OP AMP, whereby said output of said OP AMP is driven to equal VX;
a load impedance connected at one end to said OP AMP output;
said voltage divider and said load impedance having values scaled so that VX replicates the output of an emulated impedance of predetermined reactance and magnitude;
said voltage divider including impedances KZa/K−
1 and KZb/K−
1 connected in series, and said load impedance including an impedance KZb, K being a numerical constant.
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20. An impedance emulating device, including:
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a voltage divider having a midpoint node at voltage VX;
an OP AMP having one input connected to VX and the other input connected to the output of said OP AMP, whereby said output of said OP AMP is driven to equal VX;
a load impedance connected at one end to said OP AMP output;
said voltage divider and said load impedance having values scaled so that VX replicates the output of an emulated impedance of predetermined reactance and magnitude;
the positive input of said OP AMP being, connected to VX and the negative input of said OP AMP being connected to the output of said OP AMP.
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21. A impedance emulating device, including:
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a voltage divider connected between a voltage Supply and ground and having a midpoint node at voltage VX;
an amplifier having an input connected to VX and an output VY;
a load impedance connected between VY and said voltage supply;
said voltage divider and said load impedance having values scaled so that VY replicates the output of an emulated impedance of predetermined reactance and magnitude;
said voltage divider includes impedances R1 and C1 connected in series between said voltage supply and ground, said amplifier has a gain of −
N, and said emulated impedance has a resistance value R4;
- View Dependent Claims (22, 23)
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23. The impedance emulating device of claim 21, further including a further impedance emulating device for creating said impedance C1.
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24. In an integrated circuit construction, a method for emulating a large reactive impedance, comprising the steps of:
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providing a voltage divider comprised of at least one impedance having a relative component, said voltage divider having a midpoint node at voltage VX;
connecting one input of an OP AMP to VX and the other input connected to the output of said OP AMP, whereby said output of said OP AMP is driven to equal VX;
connecting a load impedance at one end to said OP AMP output;
said voltage divider and said load impedance having values scaled so that VX replicates the output of an emulated impedance of predetermined reactance and magnitude. - View Dependent Claims (25)
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Specification