OP162 Datasheet, PDF (13/16 Pages) Analog Devices – 15 MHz Rail-to-Rail Operational Amplifiers

OP162/OP262/OP462
The differential gain of the circuit is determined by R_G, where:
2
A_DIFF = 1 + _RG
with the R_G resistor value in kW. Removing R_G will set the cir-
cuit gain to unity.
The fourth op amp, OP462-D, is optional and is used to im-
prove CMRR by reducing any input capacitance to the ampli-
fier. By shielding the input signal leads and driving the shield
with the common-mode voltage, input capacitance is eliminated
at common-mode voltages. This voltage is derived from the
midpoint of the outputs of OP462-A and OP462-B by using two
10 kW resistors followed by OP462-D as a unity gain buffer.
It is important to use 1% or better tolerance components for the
2 kW resistors, as the common-mode rejection is dependent on
their ratios being exact. A potentiometer should also be con-
nected in series with the OP462-C noninverting input resistor to
ground to optimize common-mode rejection.
The circuit in Figure 41 was implemented to test its settling
time. The instrumentation amp was powered with ± 5 V, so the
input step voltage went from –5 V to +4 V to keep the OP462
within its input range. Therefore, the 0.05% settling range is
when the output is within 4.5 mV. Figure 42 shows the positive
slope settling time to be 1.8 ms, and Figure 43 shows a settling
time of 3.9 ms for the negative slope.
5mV
2V
100
90
10
0%
1␮s
Figure 42. Positive Slope Settling Time
5mV
2V
100
90
Direct Access Arrangement
Figure 44 shows a schematic for a +5 V single supply transmit/
receive telephone line interface for 600 W transmission systems.
It allows full duplex transmission of signals on a transformer
coupled 600 W line. Amplifier A1 provides gain that can be
adjusted to meet the modem output drive requirements. Both
A1 and A2 are configured so as to apply the largest possible
differential signal to the transformer. The largest signal available
on a single +5 V supply is approximately 4.0 V p-p into a 600 W
transmission system. Amplifier A3 is configured as a difference
amplifier to extract the receive information from the transmis-
sion line for amplification by A4. A3 also prevents the transmit
signal from interfering with the receive signal. The gain of A4
can be adjusted in the same manner as A1’s to meet the modem’s
input signal requirements. Standard resistor values permit the
use of SIP (Single In-line Package) format resistor arrays. Couple
this with the OP462 14-lead SOIC or TSSOP package and this
circuit can offer a compact solution.
TO TELEPHONE
LINE
1:1
Z_O
600⍀
6.2V
6.2V
T1
MIDCOM
671-8005
R3
360⍀
P1
TX GAIN
ADJUST
R2
9.09k⍀
2k⍀
2
1
R5
A1 ₃
10k⍀
R1
10k⍀
C1
0.1␮F
TRANSMIT
TXA
R6
10k⍀
7
6
A2 ₅
5V DC
R7
10k⍀
10␮F
R8
10k⍀
R9
10k⍀
R10
10k⍀
R11
10k⍀
2
3 ^{A3 1}
A1, A2 = 1/2 AD8532
A3, A4 = 1/2 AD8532
R12
10k⍀
R13
10k⍀
P2
RX GAIN
R14 ^ADJUST
14.3k⍀
RECEIVE
RXA
6
5 ^A4
2k⍀
7
C2
0.1␮F
Figure 44. A Single-Supply Direct Access Arrangement for
Modems
10
0%
1µ␮ss
Figure 43. Negative Slope Settling Time
REV. D
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