AD8042AN Analog Devices Inc, AD8042AN Datasheet - Page 14

• Manufacturer Part Number: AD8042AN
• Description: IC OPAMP VF R-R DUAL LP 8DIP
• Manufacturer: Analog Devices Inc

Specifications of AD8042AN

• Slew Rate: 225 V/µs
• Rohs Status: RoHS non-compliant
• Design Resources: Single-Ended-to-Differential Converters for Voltage Output and Current Output DACs Using AD8042 (CN0143)
• Amplifier Type: Voltage Feedback
• Number Of Circuits: 2
• Output Type: Rail-to-Rail
• -3db Bandwidth: 170MHz
• Current - Input Bias: 1.2µA
• Voltage - Input Offset: 3000µV
• Current - Supply: 6mA
• Current - Output / Channel: 50mA
• Voltage - Supply, Single/dual (±): 3 V ~ 12 V, ±1.5 V ~ 6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Through Hole
• Package / Case: 8-DIP (0.300", 7.62mm)
• Op Amp Type: Voltage Feedback
• No. Of Amplifiers: 2
• Bandwidth: 160MHz
• Supply Voltage Range: 3V To 12V
• Amplifier Case Style: DIP
• No. Of Pins: 8
• Gain Bandwidth Product: -
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

AD8042
Single-Ended-to-Differential Driver
Using a cross-coupled, single-ended-to-differential converter
(SEDC), the AD8042 makes a good general-purpose differential
line driver. This SEDC can be used for applications such as
driving Category-5 (CAT-5) twisted pair wires. Figure 39 shows
a configuration for a circuit that performs this function that can
be used for video transmission over a differential pair or various
data communication purposes.
Each of the op amps of the AD8042 is configured as a unity gain
follower by the feedback resistors (R
drives the other as a unity gain inverter via R
symmetrical circuit.
If the noninverting input of AMP2 is grounded and a small
positive signal is applied to the noninverting input of AMP1,
the output of AMP1 is driven to saturation in the positive
direction and the input of AMP2 is driven to saturation in the
negative direction. This is similar to the way a conventional op
amp behaves without any feedback.
If a resistor (R
noninverting input of AMP1, negative feedback is provided, which
closes the loop. An input resistor (R
like a conventional inverting op amp configuration with
differential outputs.
The gain of this circuit from input to either output is ±R
the single-ended-to-differential gain is 2 × R
circuit the advantage of being able to adjust its gain by changing
a single resistor.
V
IN
AD8042
Figure 39. Single-Ended-to-Differential Twisted Pair Line Driver
49.9Ω
100Ω
1kΩ
R
IN
1kΩ
R
F
6
5
) is connected from the output of AMP2 to the
B
3
2
AMP2
AMP1
–5V
+5V
1kΩ
1kΩ
R
R
8
4
A
A
1kΩ
7
1
R
0.1µF
0.1µF
B
1kΩ
R
F
10µF
10µF
60.4Ω
60.4Ω
IN
A
). Each op amp output also
) makes the circuit look
50m
F
B
/R
, creating a totally
B
IN
. This gives the
121Ω
F
/R
IN
V
Rev. E | Page 14 of 16
, or
OUT
The cable has a characteristic impedance of about 120 Ω. Each
driver output is back terminated with a pair of 60.4 Ω resistors
to make the source look like 120 Ω. The receive end is terminated
with 121 Ω, and the signal is measured differentially with a pair
of scope probes. One channel on the oscilloscope is inverted
and then the signals are added.
Figure 40 shows the results of the circuit in Figure 39 driving
50 meters of CAT-5 cable.
Single-Supply Differential A/D Driver
The single-ended-to-differential converter circuit is also useful
as a differential driver for video speed, single-ended, differential
input ADCs. Figure 41 is a schematic that shows such a circuit
differentially driving an AD9220, a 12-bit, 10 MSPS ADC.
V
IN
Figure 41. AD8042 Differential Driver for the
2.49kΩ
2.49kΩ
0.1µF
AD8042
V
OUT
V
+5V
IN
+5V
100
0%
90
10
1kΩ
Figure 40. Differential Driver Frequency Response
0.1µF
1V
1kΩ
6
5
3
2
+5V
0.1µF
1kΩ
1kΩ
8
4
0.1µF
CLOCK
1kΩ
1kΩ
1
7
0.1µF
10/16
0.1µF
200mV
200mV
0.1µF
18
17
22
1
VINA
VINB
CAPT
CAPB
VREF
SENSE
CML
CLK
REFCOM DVSS AVSS AVSS
AD9220
28
DVDD
+5V
19
0.1µF
27
12-Bit, 10 MSPS ADC
AD9220
15
AVDD
+5V
50ns
25
0.1µF
26
AVDD
BIT 10
BIT 11
BIT 12
16
+5V
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
BIT 9
OTR
0.1µF
14
13
12
11
10
9
8
7
6
5
4
3
2