ad713knz Analog Devices, Inc., ad713knz Datasheet - Page 10

• Manufacturer Part Number: ad713knz
• Description: Quad Precision, Low Cost, High Speed, Bifet Op Amp
• Manufacturer: Analog Devices, Inc.

AD713
Driving A Large Capacitive Load
The circuit of Figure 14 employs a 100
enables the amplifier to drive capacitive loads exceeding 1500 pF;
the resistor effectively isolates the high frequency feedback from
the load and stabilizes the circuit. Low frequency feedback is
returned to the amplifier summing junction via the low pass filter
formed by the 100
Figure 15 shows a typical transient response for this connection.
Trim
Resistor SD
R1
R2
Table II. Recommended Trim Resistor Values vs.
Grades for AD7545 for V
JN/AQ/
500
150
series resistor and the load capacitance, C1.
KN/BQ/
TD
200
68
D
= 5 V
LN/CQ/
UD
100
33
isolation resistor which
GLN/GCQ/
GUD
20
6.8
CMOS DAC APPLICATIONS
The AD713 is an excellent output amplifier for CMOS DACs.
It can be used to perform both 2 and 4 quadrant operation. The
output impedance of a DAC using an inverted R-2R ladder
approaches R for codes containing many “1”s, 3R for codes con-
taining a single “1” and infinity for codes containing all zeros.
For example, the output resistance of the AD7545 will modu-
late between 11 k and 33 k . Therefore, with the DAC’s
internal feedback resistance of 11 k , the noise gain will vary
from 2 to 4/3. This changing noise gain modulates the effect of
the input offset voltage of the amplifier, resulting in nonlinear
DAC amplifier performance. The AD713, with its guaranteed
1.5 mV input offset voltage, minimizes this effect achieving
12-bit performance.
Figures 16 and 17 show the AD713 and a 12-bit CMOS DAC,
the AD7545, configured for either a unipolar binary (2-quadrant
multiplication) or bipolar (4-quadrant multiplication) operation.
Capacitor C1 provides phase compensation which reduces over-
shoot and ringing.