OPA340NA-250 Datasheet, PDF (11/28 Pages) Texas Instruments – SINGLE-SUPPLY, RAIL-TO-RAIL OPERATIONAL AMPLIFIERS MicroAmplifier™ Series

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One method of improving capacitive load drive in the
unity gain configuration is to insert a 10Ω to 20Ω
resistor in series with the output, as shown in
Figure 26. This significantly reduces ringing with large
capacitive loads. However, if there is a resistive load
in parallel with the capacitive load, it creates a
voltage divider introducing a dc error at the output
and slightly reduces output swing. This error may be
insignificant. For instance, with R_L = 10kΩ and R_S =
20Ω, there is only about a 0.2% error at the output.
V+
R_S
OPAx340
V_OUT
V_IN
10W to
20W
R_L
C_L
Figure 26. Series Resistor in Unity-Gain
Configuration Improves Capacitive Load Drive
OPA340
OPA2340
OPA4340
SBOS073B – SEPTEMBER 1997 – REVISED NOVEMBER 2007
DRIVING A/D CONVERTERS
OPA340 series op amps are optimized for driving
medium speed (up to 100kHz) sampling A/D
converters. However, they also offer excellent
performance for higher speed converters. The
OPA340 series provides an effective means of
buffering the A/D’s input capacitance and resulting
charge injection while providing signal gain. Figure 27
and Figure 28 show the OPA340 driving an
ADS7816. The ADS7816 is a 12-bit, micro-power
sampling converter in the tiny MSOP-8 package.
When used with the miniature package options of the
OPA340 series, the combination is ideal for
space-limited and low-power applications. For further
information consult the ADS7816 data sheet. With the
OPA340 in a noninverting configuration, an RC
network at the amplifier’s output can be used to filter
high-frequency noise in the signal (see Figure 27). In
the inverting configuration, filtering may be
accomplished with a capacitor across the feedback
resistor (see Figure 28).
+5V
0.1mF
0.1mF
V_IN
V_IN = 0V to 5V for
0V to 5V output.
OPA340
500W
3300pF
8 V+
+In
2
-In
3
ADS7816
12-Bit A/D
GND 4
RC network filters high frequency noise.
1 V_REF
7
DCLOCK
6
D_OUT
5
CS/SHDN
Serial
Interface
NOTE: A/D Input = 0 to V_REF
Figure 27. OPA340 in Noninverting Configuration Driving ADS7816
Copyright © 1997–2007, Texas Instruments Incorporated
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