DG408, DG409
Test Circuits and Waveforms
5V +15V
V
IN
S
1
EN
V+
A
2
V
O
D
SIGNAL
GENERATOR
A
2
A
1
A
0
GND
V
-
GND
R
L
A
0
V
-
D
CHANNEL
SELECT
A
1
EN
V+
S
1
|
|
S
8
IMPEDANCE
ANALYZER
(Continued)
3V OR 0V
+15V
-
15V
ANALYZER
V
OUT
INSERTION LOSS = 20 Log -----------------
V
IN
-
15V
FIGURE 7. INSERTION LOSS
FIGURE 8. SOURCE/DRAIN CAPACITANCES
Typical Applications
Overvoltage Protection
A very convenient form of overvoltage protection consists of
adding two small signal diodes (1N4148, 1N914 type) in
series with the supply pins (see Figure 9). This arrangement
effectively blocks the flow of reverse currents. It also floats
the supply pin above or below the normal V+ or V- value. In
this case the overvoltage signal actually becomes the power
supply of the IC. From the point of view of the chip, nothing
has changed, as long as the difference V+ - (V-) doesn’t
exceed 44V. The addition of these diodes will reduce the
analog signal range to 1V below V+ and 1V above V-, but it
preserves the low channel resistance and low leakage
characteristics.
Typical application information is for Design Aid Only, not
guaranteed and not subject to production testing.
V+
1N4148
S
X
D
DG408
V
G
1N4148
V
-
FIGURE 9. OVERVOLTAGE PROTECTION USING BLOCKING
DIODES
8
FN3283.8
June 13, 2006
INTERSIL [ INTERSIL CORPORATION ]
