clc428 National Semiconductor Corporation, clc428 Datasheet - Page 5

• Manufacturer Part Number: clc428
• Description: Dual Wideband, Low-noise, Voltage Feedback Op Amp
• Manufacturer: National Semiconductor Corporation

Analog Delay Circuit (All-Pass Network)
The circuit in Figure 1 implements an all-pass network using
the CLC428. A wide bandwidth buffer (CLC111) drives the
circuit and provides a high input impedence for the source.
As shown in Figure 2, the circuit provides a
13.1ns delay (with R =40.2 , C=47pF). R
be of equal and low value for parasitic insensitive opera-
tion. The circuit gain is +1 and the delay is determined by
the following equations.
where T
provides a typical delay of 2.8ns at its -3dB point.
Full Duplex Digital or Analog Transmission
Simultaneous transmission and reception of analog or
digital signals over a single coaxial cable or twisted-pair
line can reduce cabling requirements. The CLC428's wide
bandwidth and high common-mode rejection in a differen-
tial amplifier configuration allows full duplex transmission
of video, telephone, control and audio signals.
In the circuit shown in Figure 3, one of the CLC428's amps
is used as a "driver" and the other as a difference
"receiver" amplifier. The output impedance of the "driver"
is essentially zero. The two R's are chosen to match the
characteristic impedance of the transmission line. The
"driver" op amp gain can be selected for unity or greater.
Receiver amplifier A
forms differential amplifier for the signals transmitted by
driver A
R
g
, receiver A
d
1
T
is the delay of the op amp at A
(B
delay
d
1
). If the coax cable is lossless and R
360
2
1
(B
2 2
2
d
df
) will then reject the signals from driver
RC T
2
;
(B
Figure 1
Figure 2
2
) is connected across R and
d
V
=+1. The CLC428
f
and R
g
f
should
equals
Eq. 1
Eq. 2
5
A
output of the receiver amplifier will be:
Care must be given to layout and component placement to
maintain a high frequency common-mode rejection. The
plot of Figure 4 shows the simultaneous reception of
signals transmitted at 1MHz and 10MHz.
Five Decade Integrator
A composite integrator, as shown in Figure 5, uses the
CLC428 dual op amp to increase the circuits' usable
frequency range of operation. The transfer function of this
circuit is:
A resistive divider made from the 143
resistors was chosen to reduce the loop-gain and stabilize
the network. The CLC428 composite integrator provides
integration over five decades of operation. R and C set the
integrator's gain. Figure 6 shows the frequency and phase
response of the circuit in Figure 5 with R = 44.2
C = 360pF.
1
V
out
(B
1
A B
) and pass the signals from driver B
2
1
V
in
A B
V
o
1
RC
1
Figure 3
Figure 4
Figure 5
R
R
g
f
V dt
in
2
1
V
in
B A
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1
Eq. 4
R
R
g
f
1
and 60.4
(A
1
). The
Eq. 3
and