Application Hints

GENERAL INFORMATION

These devices are monolithic quad JFET analog switches

with “ON” resistances which are essentially independent of

analog voltage or analog current. The leakage currents are

typically less than 1 nA at 25˚C in both the “OFF”and “ON”

switch states and introduce negligible errors in most applica-

tions. Each switch is controlled by minimum TTL logic levels

at its input and is designed to turn “OFF” faster than it will

turn “ON.” This prevents two analog sources from being tran-

siently connected together during switching. The switches

were

designed

for

applications

which

require

break-before-make action, no analog current loss, medium

speed switching times and moderate analog currents.

Because these analog switches are JFET rather than

CMOS, they do not require special handling.

LOGIC INPUTS

The logic input (IN), of each switch, is referenced to two for-

ward diode drops (1.4V at 25˚C) from the reference supply

(V

logic families. For normal operation, the logic “0” voltage can

range from 0.8V to −4.0V with respect to V

voltage can range from 2.0V to 6.0V with respect to V

vided V

is greater than (V

the input voltage exceeds 6.0V or −4.0V with respect to V

a resistor in series with the input should be used to limit the

input current to less than 100µA.

ANALOG VOLTAGE AND CURRENT

Analog Voltage

Each switch has a constant “ON” resistance (R

voltages from (V

greater than (V

dent of the logic input voltage. For analog voltages less than

(V

though the switch will not operate normally when the analog

voltage is out of the previously mentioned range, the source

voltage can go to either (V

is more positive, and can go as negative as V

struction. The drain (D) voltage can also go to either

(V

go as negative as (V

Analog Current

With the source (S) positive with respect to the drain (D), the

R

region. However, if the drain is positive with respect to the

source and a small analog current loss at high analog cur-

rents (Note 6) is tolerable, a low R

analog currents greater than 5 mA at 25˚C.

Slew Rate of Analog

Voltage Above Which

Signal Loading Occurs

DS005667-35

Small Signal Response

DS005667-36

Maximum Accurate

Analog Current

vs Temperature

DS005667-37

Logical “1” Input Bias

Current

DS005667-38

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