OPA4342EA BURR-BROWN [Burr-Brown Corporation], OPA4342EA Datasheet - Page 10

• Manufacturer Part Number: OPA4342EA
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

Overshoot vs Capacitive Load.” In unity-gain configura-
tions, capacitive load drive can be improved by inserting a
small (10 to 20 ) resistor, R
shown in Figure 5. This significantly reduces ringing while
maintaining dc performance for purely capacitive loads.
However, if there is a resistive load in parallel with the
capacitive load, a voltage divider is created, introducing a dc
error at the output and slightly reducing the output swing.
The error introduced is proportional to the ratio R
is generally negligible.
FIGURE 5. Series Resistor in Unity-Gain Configuration
FIGURE 6. OPA342 in Noninverting Configuration Driving ADS7822.
FIGURE 7. Speech Bandpass Filtered Data Acquisition System.
V
IN
Microphone
NOTE: (1) Electret microphone
powered by R
Electret
Improves Capacitive Load Drive.
®
OPA342
V
0V to 5V output.
1.5k
IN
R
OPA342, 2342, 4342
V+
(1)
= 0V to 5V for
1
1
.
V
IN
1000pF
1M
C
1M
R
R
1
2
3
10 to
20
R
RC network filters high frequency noise.
S
S
, in series with the output, as
OPA342
20k
20k
R
R
OPA2342
5
4
R
1/2
L
100k
R
6
500
G = 100
3300pF
C
S
L
51k
V+ = +2.7V to 5V
/ R
R
7
V
C
L
OUT
2
, and
150k
1000pF
R
+In
8
10
2
–In
DRIVING A/D CONVERTERS
The OPA342 series op amps are optimized for driving
medium-speed sampling ADCs. The OPA342 op amps buffer
the ADC’s input capacitance and resulting charge injection
while providing signal gain.
Figures 6 shows the OPA342 in a basic noninverting con-
figuration driving the ADS7822. The ADS7822 is a 12-bit,
micro-power sampling converter in the MSOP-8 package.
When used with the low-power, miniature packages of the
OPA342, the combination is ideal for space-limited, low-
power applications. In this configuration, an RC network at
the ADC’s input can be used to filter charge injection.
Figure 7 shows the OPA2342 driving an ADS7822 in a
speech bandpass filtered data acquisition system. This small,
low-cost solution provides the necessary amplification and
signal conditioning to interface directly with an electret
microphone. This circuit will operate with V
+5V with less than 500 A quiescent current.
3
8
OPA2342
+5V
510k
12-Bit A/D
ADS7822
33pF
R
1/2
C
V+
0.1 F
9
3
GND
4
+IN
2
–IN
Passband 300Hz to 3kHz
V
CS/SHDN
REF
DCLOCK
3
1
12-Bit A/D
ADS7822
D
1
V
0.1 F
OUT
NOTE: A/D Input = 0 to V
REF
4
8
7
6
5
V +
GND
7
6
5
DCLOCK
D
CS/SHDN
OUT
Interface
Serial
REF
Serial
Interface
S
= +2.7V to