MOS threshold control circuit
First Claim
1. Apparatus for controlling a threshold voltage of a circuit including an MOS operating device having a back gate, comprising:
- a reference stage including an input, an output and an MOS reference device having a back gate;
means for applying a reference voltage VR to the input of said reference stage, said reference voltage VR being equal to the desired circuit threshold voltage; and
feedback means for providing a control voltage to the back gate of said MOS reference device for maintaining a prescribed relationship between said reference voltage and a voltage VX at said output, said control voltage being coupled to the back gate of said MOS operating device.
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Accused Products
Abstract
A circuit for controlling the circuit thresholds on an MOS integrated circuit takes advantage of the fact that all MOS devices of a particular type on the same chip have nearly identical characteristics. The circuit thresholds are varied by applying a control voltage to the back gate of an MOS device in each stage to be controlled. The control voltage is generated in a reference stage which utilizes a feedback loop to servo the back gate voltage of an MOS transistor in the loop. A reference voltage equal to the desired circuit threshold votlage is applied to the input of the reference stage. The reference voltage and the reference stage output are applied to an amplifier in the feedback loop. The amplifier applies to the back gate of the MOS transistor in the reference stage a control voltage that tends to equalize or establish a desired offset between the reference voltage and the reference stage output. The control voltage applied to the reference stage back gate is coupled to the back gate of the MOS transistor in each operating stage. The threshold control circuit is particularly useful in CMOS circuits, but can be utilized in any MOS circuit having an MOS transistor with an accessible back gate.
74 Citations
14 Claims
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1. Apparatus for controlling a threshold voltage of a circuit including an MOS operating device having a back gate, comprising:
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a reference stage including an input, an output and an MOS reference device having a back gate; means for applying a reference voltage VR to the input of said reference stage, said reference voltage VR being equal to the desired circuit threshold voltage; and feedback means for providing a control voltage to the back gate of said MOS reference device for maintaining a prescribed relationship between said reference voltage and a voltage VX at said output, said control voltage being coupled to the back gate of said MOS operating device. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A monolithic integrated circuit comprising:
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at least one MOS operating stage including an MOS device having a back gate; a reference stage including an input, an output and an MOS reference device having a back gate; means for applying a reference voltage VR to the input of said reference stage, said reference voltage VR being equal to a desired operating stage threshold voltage; and feedback means providing a control voltage to the back gate of said MOS reference device for maintaining a prescribed relationship between said reference voltage and a voltage VX at said output, said control voltage establishing the threshold voltage of said reference stage and being coupled to the back gate of said MOS operating device. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A monolithic integrated circuit comprising:
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a plurality of MOS operating stages, each including an MOS device having a back gate; a reference stage including an input, an output and an MOS reference device having a back gate; means for applying a reference voltage VR to the input of said reference stage, said reference voltage VR being equal to a desired operating stage threshold voltage; amplifier means for applying a control voltage to the back gate of said MOS reference device; means coupling said reference voltage VR to said amplifier means; means coupling a voltage VX at said output plus an offset voltage VA to said amplifier means, said amplifier means being responsive to a difference between said reference voltage VR and the sum of said output voltage VX and said offset voltage VA for applying a control voltage to the back gate of said MOS reference device so as to reduce said difference, said control voltage being coupled to the back gate of said MOS device in each MOS operating stage. - View Dependent Claims (14)
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Specification