AD713 Analog Devices, AD713 Datasheet - Page 12

• Manufacturer Part Number: AD713
• Description: Precision, High Speed, BiFET Quad Op Amp
• Manufacturer: Analog Devices

Specifications of AD713

• -3db Bandwidth: 4MHz
• Slew Rate: 20V/µs
• Vos: 300µV
• Ib: 40pA
• # Opamps Per Pkg: 4
• Input Noise (nv/rthz): 16nV/rtHz
• Vcc-vee: 9V to 36V
• Isy Per Amplifier: 3mA
• Packages: DIP,SOIC

AD713
A HIGH SPEED INSTRUMENTATION AMPLIFIER
CIRCUIT
The instrumentation amplifier circuit shown in Figure 33 can
provide a range of gains from unity up to 1000 and higher using
only a single AD713. The circuit bandwidth is 1.2 MHz at a gain
of 1 and 250 kHz at a gain of 10; settling time for the entire
circuit is less than 5 μs to within 0.01% for a 10 V step, (G = 10).
Other uses for Amplifier A4 include an active data guard and an
active sense input.
Table 4 provides a performance summary for this circuit. Figure 34
shows the pulse response of this circuit for a gain of 10.
Table 4. Performance Summary for the High Speed
Instrumentation Amplifier Circuit
Gain
1
2
10
1
COM
–IN
+IN
+V
–V
NC = no connect.
R
G
S
S
Figure 34. Pulse Response of High Speed Instrumentation Amplifier,
100
0%
90
10
0.1µF
0.1µF
3
2
6
5
• • • •
• • • •
Figure 33. High Speed Instrumentation Amplifier Circuit
R
NC
20 kΩ
4.04 kΩ
7.5pF
7.5pF
G
A1
A2
1
• • • •
• • • •
AD713
AD713
+
+
10kΩ
10kΩ
1µF
1µF
1/4
1/4
5V
1
7
• • • •
• • • •
CIRCUIT GAIN =
Bandwidth
1.2 MHz
1.0 MHz
0.25 MHz
• • • •
• • • •
10kΩ**
10kΩ**
AD713
PIN 4
AD713
PIN 11
5pF
(TRIM FOR BEST SETTLING TIME)
• • • •
• • • •
Gain = 10
**
*
VOLTRONICS SP20 TRIMMER CAPACITOR
OR EQUIVALENT
RATIO MATCHED 1% METAL FILM
RESISTORS
*1.5pF TO 20pF
10kΩ**
• • • •
• • • •
10
14
9
AD713
20,000
R
10kΩ**
1/4
G
A3
AD713
• • • •
• • • •
Settling Time (0.01%)
2 μs
2 μs
2 μs
A4
+ 1
1/4
13
12
• • • •
• • • •
8
2µs
• • • •
• • • •
SENSE
TO BUFFERED
VOLTAGE
REFERENCE
OR REMOTE
GROUND SENSE
• • • •
• • • •
Rev. F | Page 12 of 20
A HIGH SPEED 4-OP-AMP CASCADED AMPLIFIER
CIRCUIT
Figure 35 shows how the four amplifiers of the AD713 can be
connected in cascade to form a high gain, high bandwidth
amplifier. This gain of 100 amplifier has a −3 dB bandwidth
greater than 600 kHz.
HIGH SPEED OP AMP APPLICATIONS AND
TECHNIQUES
DAC Buffers (I-to-V Converters)
The wide input dynamic range of JFET amplifiers makes them
ideal for use in both waveform reconstruction and digital audio
DAC applications. The AD713, in conjunction with a 16-bit
DAC, can achieve 0.0016% THD without requiring the use of a
deglitcher in digital audio applications.
Driving the Analog Input of an Analog-to-Digital
Converter
An op amp driving the analog input of an analog-to-digital
converter (ADC), such as that shown in Figure 37, must be
capable of maintaining a constant output voltage under dynami-
cally changing load conditions. In successive approximation
converters, the input current is compared to a series of switched
trial currents. The comparison point is diode clamped but may
vary by several hundred millivolts, resulting in high frequency
modulation of the analog-to-digital input current. The output
impedance of a feedback amplifier is made artificially low by its
INPUT
1kΩ
OPTIONAL V
ADJUSTMENT
–V
S
3
2
2.15kΩ
100kΩ
Figure 35. High Speed 4-Op-Amp Cascaded Amplifier Circuit
LOW DISTORTION
SINEWAVE INPUT
AD713
+V
22MΩ
4
1/4
S
+V
OS
1
S
1kΩ
1kΩ
1µF
4-OP-AMP CASCADED AMPLIFIER
GAIN = 100
BANDWIDTH (–3dB) = 632kHz
5
6
2.15kΩ
TO SPECTRUM ANALYZER
1kΩ
Figure 36. THD Test Circuit
AD713
0.1µF
1/4
AD713
7
1kΩ
1/4
+V
–V
11
4
100kΩ
S
S
10
9
2.15kΩ
NULL
ADJUST
AD713
+
1/4
+
10kΩ
1µF
1µF
8
1kΩ
ERROR SIGNAL
(ERROR/11)
10kΩ
OUTPUT
0.1µF
0.1µF
2.15kΩ
12
13
–V
11
AD713
100pF
S
1µF
1/4
14
+
OUTPUT
0.1µF