During the sample-to-hold transition, a small amount of charge is injected onto the hold capacitor, mostly because of the stray capacitance of the switch that creates small level changes when transitioning between states. The resulting dc offset is typically referred to as pedestal error. This error contributes to the offset error of the system. The pedestal error, ΔV_OUT, is the measured offset voltage resulting from charge injection when the switch transitions to hold state. ΔV_OUT is related to charge injection through Equation 2.

Equation 2.

where

• Q is the injected charge coulombs.
• C is the value of the hold capacitor in farads.

In most solid-state switch data sheets, charge injection is graphed with respect to supply voltage, analog input, or temperature. A charge injection value of 3 pC is typical in many solid-state switches under the conditions: 25°C, 5-V supply, and 0-V analog input.