Capacitance measuring device
First Claim
1. A capacitance measuring device comprising a MOS transistor having a source, drain, and gate;
- a first capacitor C1 connected between said gate and said drain so that charge is coupled from said drain onto said gate;
a second capacitor C2 for connection to a source of gate voltage VG and connected to said gate;
one of said first and second capacitors having a known capacitance and the other of said first and second capacitors having an unknown capacitance;
means for applying a variable known DC voltage between said source and drain to cause a saturation current to flow therebetween; and
means for determining the ratio δ
VG /δ
Vd for said saturation current, where VG is the applied gate voltage, and Vd is the drain voltage;
said unknown capacitance thereby being derivable from the relationship C1 /C2 =-δ
VG /δ
Vd.
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Accused Products
Abstract
A capacitance measuring device comprises a MOS transistor having a source, drain, and gate; a first capacitor C1 connected between said gate and said drain so that charge is coupled from said drain onto said gate; and a second capacitor C2 for connection to a source of gate voltage VG and connected to said gate. One of the first and second capacitors has a known capacitance and the other has an unknown capacitance. A DC voltage is supplied between the source and drain to cause a saturation current to flow therebetween. The ratio δVG /δVd for the saturation current, where VG is the applied gate voltage, and Vd is the drain voltage is determined and the unknown capacitance is derived from the relationship C1 /C2 =-δVG /δVd.
26 Citations
10 Claims
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1. A capacitance measuring device comprising a MOS transistor having a source, drain, and gate;
- a first capacitor C1 connected between said gate and said drain so that charge is coupled from said drain onto said gate;
a second capacitor C2 for connection to a source of gate voltage VG and connected to said gate;
one of said first and second capacitors having a known capacitance and the other of said first and second capacitors having an unknown capacitance;
means for applying a variable known DC voltage between said source and drain to cause a saturation current to flow therebetween; and
means for determining the ratio δ
VG /δ
Vd for said saturation current, where VG is the applied gate voltage, and Vd is the drain voltage;
said unknown capacitance thereby being derivable from the relationship C1 /C2 =-δ
VG /δ
Vd. - View Dependent Claims (2, 3, 4, 5, 10)
- a first capacitor C1 connected between said gate and said drain so that charge is coupled from said drain onto said gate;
- 6. A method of measuring capacitance, comprising isolating a gate region of a MOS device from exterior biasing with a first capacitor, coupling charge between a drain and said gate of said MOS device with a second capacitor, one of said first and second capacitors having an unknown capacitance, and measuring the rate of change of gate voltage with respect to drain voltage at saturation current to derive said unknown capacitance therefrom.
Specification