AD713
MEASURING AD713 SETTLING TIME
The error signal is thus clamped twice: once to prevent overload-
ing amplifier A2 and then a second time to avoid overloading the
oscilloscope preamp. A Tektronix oscilloscope preamp type 7A26
was carefully chosen because it recovers from the approximately
0.4 V overload quickly enough to allow accurate measurement
of the AD713’s 1 µs settling time. Amplifier A2 is a very high
speed FET input op amp; it provides a voltage gain of 10, am-
plifying the error signal output of the AD713 under test (providing
an overall gain of 5).
The photos of Figures 2 and 3 show the dynamic response of
the AD713 while operating in the settling time test circuit of
Figure 1. The input of the settling time fixture is driven by a
flat-top pulse generator. The error signal output from the false
summing node of A1, the AD713 under test, is clamped, ampli-
fied by op amp A2 and then clamped again.
Figure 3. Settling Characteristics to –10 V Step.
Upper Trace: Output of AD713 Under Test (5 V/div).
Lower Trace: Amplified Error Voltage (0.01%/ div)
POWER SUPPLY BYPASSING
The power supply connections to the AD713 must maintain a
low impedance to ground over a bandwidth of 4 MHz or more.
This is especially important when driving a significant resistive
or capacitive load, since all current delivered to the load comes
from the power supplies. Multiple high quality bypass capacitors
are recommended for each power supply line in any critical
application. A 0.1 µF ceramic and a 1 µF electrolytic capacitor
as shown in Figure 4 placed as close as possible to the amplifier
(with short lead lengths to power supply common) will assure
adequate high frequency bypassing in most applications. A
minimum bypass capacitance of 0.1 µF should be used for any
application.
Figure 1. Settling Time Test Circuit
Figure 2. Settling Characteristics 0 V to +10 V Step.
Upper Trace: Output of AD713 Under Test (5 V/div).
Lower Trace: Amplified Error Voltage (0.01%/div)
Figure 4. Recommended Power Supply Bypassing
REV. C
–7–
ADI [ ADI ]
