adg452 Analog Devices, Inc., adg452 Datasheet - Page 12

• Manufacturer Part Number: adg452
• Description: Lc2 Mos 5 ? R Spst Switches
• Manufacturer: Analog Devices, Inc.

ADG451/ADG452/ADG453
APPLICATIONS
Figure 15 illustrates a precise, fast, sample-and-hold circuit. An
AD845
amplifier is an AD711. During track mode, SW1 is closed, and
the output, V
SW1 is opened, and the signal is held by the hold capacitor, C
V
IN
AD845
is used as the input buffer, and the output operational
+15V
–15V
Figure 15. Fast, Accurate Sample-and-Hold Circuit
OUT
, follows the input signal, V
SW2
SW1
+15V
S
S
ADG451/
ADG452/
ADG453
13
5
–15V
+5V
12
4
D
D
75Ω
R
C
C
1000pF
C
2200pF
CH
2200pF
IN
. In hold mode,
AD711
+15V
–15V
V
OUT
Rev. C | Page 12 of 16
H
.
Due to switch and capacitor leakage, the voltage on the hold
capacitor decreases with time. The ADG451/ADG452/ADG453
minimize this droop due to their low leakage specifications. The
droop rate is further minimized by the use of a polystyrene
hold capacitor. The droop rate for the circuit shown is typically
30 μV/μs.
A second switch, SW2, which operates in parallel with SW1, is
included in this circuit to reduce pedestal error. Because both
switches are at the same potential, they have a differential effect
on the op amp, AD711, which minimizes charge injection
effects. Pedestal error is also reduced by the compensation
network, R
hold time glitch while optimizing the acquisition time. Using
the illustrated op amps and component values, the pedestal
error has a maximum value of 5 mV over the ±10 V input
range. Both the acquisition and settling times are 850 ns.
C
and C
C
. This compensation network reduces the