Compensated-current mirror off-chip driver
First Claim
1. An off-chip driver circuit for integrated circuits comprising:
- a reference current amplifier circuit connected to an input voltage (Vcmn) for providing a reference current, and a reference current-voltage (Vbias2) on an output lead of the reference current amplifier circuit, an output driver circuit including a pull-up circuit stage having an input lead connected to the reference current amplifier circuit output lead and responsive to the reference current-voltage (Vbias2) to produce an output current on an output lead proportional to the reference current provided by the reference current amplifier, wherein the reference current amplifier includes first and second transistor devices connected in series to form a first current path and third and fourth transistor devices connected in series to form a second current path, wherein the reference current from the reference current amplifier flows in the first current path and the reference current has a level that is determined by the Beta of the second transistor of the first current path.
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Accused Products
Abstract
An off-chip driver circuit with compensated current source including a reference current amplifier and an output driver with a pull-up section. The reference current amplifier includes an input voltage Vcmn from an on chip current reference source. A reference current is established in the reference current amplifier by choosing the Beta of transistor in a current path. A feature of the circuit is that an output current is produced in the output lead of the driver circuit that is proportional to the current in the reference current amplifier, but with adjustments made for the supply voltage level and effective transistor channel length, Leff. Another feature of the circuit is that a reference current-voltage is established on the output lead of the reference current amplifier that is primarily determined by a multiple of the reference current but is reduced by a function of the supply voltage. In the circuit the output current of the driver is reduced linearly and predictably with the supply voltage.
17 Citations
12 Claims
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1. An off-chip driver circuit for integrated circuits comprising:
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a reference current amplifier circuit connected to an input voltage (Vcmn) for providing a reference current, and a reference current-voltage (Vbias2) on an output lead of the reference current amplifier circuit, an output driver circuit including a pull-up circuit stage having an input lead connected to the reference current amplifier circuit output lead and responsive to the reference current-voltage (Vbias2) to produce an output current on an output lead proportional to the reference current provided by the reference current amplifier, wherein the reference current amplifier includes first and second transistor devices connected in series to form a first current path and third and fourth transistor devices connected in series to form a second current path, wherein the reference current from the reference current amplifier flows in the first current path and the reference current has a level that is determined by the Beta of the second transistor of the first current path. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification