Tri-state differential amplifier
First Claim
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1. A differential amplifier having an amplify mode and a tri-state mode, comprising:
- a first transistor having a control electrode for receiving a first input signal, a first current electrode coupled to a load node, and a second current electrode;
a second transistor having a control electrode for receiving a second input signal, a first current electrode coupled to a second load node, and a second current electrode;
a third transistor having a control electrode for receiving an enable signal, a first current electrode coupled to the second current electrode of the first transistor, and a second current electrode coupled to the second current electrode of the second transistor;
a fourth transistor having a control electrode for receiving the enable signal, a first current electrode coupled to the second current electrode of the first transistor, and a second current electrode coupled to the first power supply terminal;
a fifth transistor having a control electrode for receiving the enable signal, a first current electrode coupled to the second current electrode of the second transistor, and a second current electrode coupled to the first power supply terminal;
a first switchable load coupled between a second power supply terminal and the first load node;
a second switchable load coupled between the second power supply terminal and the second load node; and
load control means for switching off the first and second switchable loads in the tri-state mode.
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Abstract
An amplifier has a pair of common source transistors in which the sources are coupled together during a first mode of operation and isolated from each other during a second mode of operation. A current source provides current between a power supply terminal and these sources during the first mode and prevents current flow therebetween during the second mode. A pair of switchable loads act as loads for the common source transistors during the first mode and are switched off during the second mode.
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Citations
8 Claims
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1. A differential amplifier having an amplify mode and a tri-state mode, comprising:
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a first transistor having a control electrode for receiving a first input signal, a first current electrode coupled to a load node, and a second current electrode; a second transistor having a control electrode for receiving a second input signal, a first current electrode coupled to a second load node, and a second current electrode; a third transistor having a control electrode for receiving an enable signal, a first current electrode coupled to the second current electrode of the first transistor, and a second current electrode coupled to the second current electrode of the second transistor; a fourth transistor having a control electrode for receiving the enable signal, a first current electrode coupled to the second current electrode of the first transistor, and a second current electrode coupled to the first power supply terminal; a fifth transistor having a control electrode for receiving the enable signal, a first current electrode coupled to the second current electrode of the second transistor, and a second current electrode coupled to the first power supply terminal; a first switchable load coupled between a second power supply terminal and the first load node; a second switchable load coupled between the second power supply terminal and the second load node; and load control means for switching off the first and second switchable loads in the tri-state mode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification