Dual SPDT switch with 1 pC charge injection
The MAX4528ESA+ is a dual SPDT analog switch from Analog Devices, configured as a 2:1 multiplexer/demultiplexer per channel. It switches signals up to 110 Ohm on-resistance max, with channel-to-channel matching of 3 Ohm — tight enough that gain error across paths stays within a few tenths of a percent in a precision signal chain. Charge injection is specified at 1 pC typical, which matters when the switch connects to a sampling capacitor — that injected charge appears as a voltage step on the hold node. For a 10 nF hold cap, 1 pC produces a 100 µV glitch; for smaller caps the error scales proportionally.
Supply flexibility and leakage floor
The 500 pA max off-leakage keeps the switch from loading the signal source when the channel is deselected. Channel capacitance (CS(off), CD(off)) is 13 pF, contributing to the off-isolation roll-off above a few MHz. For audio-band or low-frequency precision signals this is negligible; for a 10 MHz carrier the feedthrough through the parasitic capacitance may need a downstream filter.