Elantec Semiconductor, Inc.

Chor-Yin Chia

The analog demultiplexer (FIG.) includes an input amplifier (A), and output amplifiers (AMP&#x2013;AMP). The output and inverting (&#x2212;) input of amplifiers (AMP&#x2013;AMP) are connected by a respective capacitor (C&#x2013;C). Switches (S, S, etc.) connect the output of amplifier (A) to the inverting input of one of (AMP&#x2013;AMP). Switches (S, S, etc.) connect the output of one of (AMP&#x2013;AMP) to the non-inverting input of the amplifier A. Switches (S, S, etc.) and (S, S, etc.) open and close together in pairs. With feedback from the output of (AMP&#x2013;AMP) through (A), the gain and any offset of (AMP&#x2013;AMP) is divided down by the gain of (A). Amplifier (A) has capacitors (Cand C) connected to its inputs. Switch (S) connects the inverting input of amplifier (A) to its output, and switch (S) connects the non-inverting input of (A) to a voltage reference (V) matching (V) applied to (AMP). Switches (S) and (S) connect (C) and (C) to the demultiplexer input (). In operation, switches (S, S, Sand S) are initially closed, while switches (S, S, etc.) are open to charge both capacitors (C) and (C) and the inputs and output of (A) to (V). Switch (S) provides feedback to divide down gain errors and offset of (A). Switches (S, S, Sand S) are then open, while one of switches (S, S, etc.) is closed with one switch (S, S, etc) to drive one of the output voltages (V&#x2013;V). With inputs and outputs of (A) and the connected (AMP&#x2013;AMP) initially be at (V), very little settling time is needed.

Analog demultiplexing

The analog demultiplexer (FIG.) includes an input amplifier (A), and output amplifiers (AMP-AMP). The output and inverting (&#x2212;) input of amplifiers (AMP-AMP) are connected by a respective capacitor (C-C). Switches (S, S, etc.) connect the output of amplifier (A) to the inverting input of one of (AMP-AMP). Switches (S, S, etc.) connect the output of one of (AMP-AMP) to the non-inverting input of the amplifier A. Switches (S, S, etc.) and (S, S, etc.) open and close together in pairs. With feedback from the output of (AMP-AMP) through (A), the gain and any offset of (AMP-AMP) is divided down by the gain of (A). Amplifier (A) has capacitors (Cand C) connected to its inputs. Switch (S) connects the inverting input of amplifier (A) to its output, and switch (S) connects the non-inverting input of (A) to a voltage reference (V) matching (V) applied to (AMP). Switches (S) and (S) connect (C) and (C) to the demultiplexer input (). In operation, switches (S, S, Sand S) are initially closed, while switches (S, S, etc.) are open to charge both capacitors (C) and (C) and the inputs and output of (A) to (V). Switch (S) provides feedback to divide down gain errors and offset of (A). Switches (S, S, Sand S) are then open, while one of switches (S, S, etc.) is closed with one switch (S, S, etc) to drive one of the output voltages (V-V). With inputs and outputs of (A) and the connected (AMP-AMP) initially be at (V), very little settling time is needed.

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Santa Clara, CA, United States of America

Chor-Yin Chia