Engineering Definitions and Terms
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IC Analog Switch Chips
Semiconductor Switch. An Analog Switch is a Linear CMOS Integrated Circuit [IC]. The actual switch is normally a produced using a MOSFET, while the control pin [or pins] is a TTL or CMOS digital input used to open or close the switch [turn on or off the FET. The Control pins in the example above are IN1 and IN2.
The Analog Switch offers high switching speed and very low on resistance,
and very low leakage current when off. The 'on' resistance determines how well the device approximates a closed mechanical switch, and the 'leakage' current determines how well the device approximates an open mechanical switch.
Analog Switch Chip
Analog switches are classified just like mechanical switches; in the example above the top circuit is a Dual Single Pole Single Throw [SPST], while the lower circuit is a Single Pole Double Throw [SPDT].
The analog switch labeled Single Switch indicates a switch controlled by a single control line, in this case the package contains two individual switches and two separate control lines. The analog switch labeled Differential Switch indicates two switches controlled by a single control line. The phrase differential is used to indicate that the switches change as a pair. As in a pair of differential lines, one positive and the other negative. However the term could include any number of switch pairs with in the same package. This particular example shows two normally closed switches [NC], but a differential switch could contain two normally open switches [NO], or one normally open switch and one normally closed switch. A differential switch only needs to have a pair on contacts controlled by a single control line.
Analog Multiplexer are Analog switches that receive more than one analog input and place one of those inputs on the output pin based on the condition of the control pins [which are normally digital controls].
Design hint; First select the required switch function. Then select the operational frequency requirements. Next select a part based on the 'on' and 'off' [leakage] resistance. Finally select the component based on package style. Analog Switch Manufacturers.
The same CMOS switch functions are available in a metal can in addition to the Dual In-line Package [DIP] shown above.
Analog Switch Chip
The same style switch is also available as two separate sets of switches; Dual Control Analog Switches [DIP package].
Commercial and Industrial temperature ranges for Integrated Circuits; [IC Temperature Ranges].
Design Hint; I/O isolation can be increased by using two switches in series, operated in phase. However the 'ON' [rds] resistance is also increased because the two switch resistances add together.
Index > Logic Design > IC Design > IC Schematics > Analog Switch
