| CPC H03K 17/6871 (2013.01) [H04L 12/40032 (2013.01); H04L 2012/40215 (2013.01); H04L 2012/40273 (2013.01)] | 20 Claims |

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1. A circuit, comprising:
a first transistor having a drain, a control terminal, and a source coupled to a voltage supply terminal;
a second transistor having a source, a control terminal, and a drain coupled to the drain of the first transistor;
a third transistor having a control terminal, having a drain coupled to the control terminal of the second transistor, and having a source coupled to a the source of the second transistor; and
a fourth transistor having a control terminal and a source coupled to the source of the second transistor, wherein the third transistor is configured to inactivate the second transistor when a voltage at a drain of the fourth transistor is above a threshold.
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