The TMUX1121, TMUX1122, or TMUX1123 switch is used in conjunction with the voltage holding capacitors (C_H) to implement the sample-and-hold circuit. The basic operation is:

1. When the switch (SW2) is closed, it samples the input voltage and charges the holding capacitors (C_H) to the input voltages values.
2. When the switch (SW2) is open, the holding capacitors (C_H) holds its previous value, maintaining stable voltage at the amplifier output (V_OUT).

Due to switch and capacitor leakage current, as well as amplifier bias current, the voltage on the hold capacitors droops with time. The TMUX1121, TMUX1122, or TMUX1123 minimize the droops due to its ultra-low leakage performance. At 25°C, the TMUX1121, TMUX1122, and TMUX1123 have extremely low leakage current at 3pA typical.

A second switch SW1 is also included to operate in parallel with SW2 to reduce pedestal error during switch toggling. Because both switches are driven at the same potential, they act as common-mode signal to the op-amp, thereby minimizing the charge injection effects caused by the switch toggling action. Compensation network consisting of R_C and C_C is also added to further reduce the pedestal error, whiling reducing the hold-time glitch and improving the settling time of the circuit. Refer to Sample and Hold Glitch Reduction for Precision Outputs Reference Design for more information on sample-and-hold circuits.