clc427 National Semiconductor Corporation, clc427 Datasheet - Page 5

• Manufacturer Part Number: clc427
• Description: Dual Voltage Feedback Amplifier For Single Supply Operation
• Manufacturer: National Semiconductor Corporation

Load Termination
Since the CLC427 design has been optimized for Single
Supply Operation, it is more capable of sourcing rather
than sinking current. For optimum performance, the load
should be tied to V
output always sources current.
Output Overdrive Recovery
When the output range of an amplifier is exceeded, time
is required for the amplifier to recover from this over
driven condition.
recovery of the CLC427 when the output is overdriven.
An input was applied in an attempt to drive the
output to twice the supply rails, V
the output limits. An inverting gain topology was used,
see Figure 2. As indicated, the CLC427 recovers within
25ns on the rising edge and within 10ns on the falling
edge.
Channel Matching
Channel matching and crosstalk rejection are largely
dependent on board layout.
dual amplifier evaluation boards are designed to produce
optimum channel matching and isolation.
matching for the CLC427 is shown in Figure 6.
The CLC427’s channel-to-channel isolation is better than
-70dB for video frequencies of 4MHz.
crosstalk vs frequency is illustrated in Figure 7. Pulsed
crosstalk is shown in Figure 8.
Figure 5: Overdrive Recovery
Figure 6: Channel Matching
V
out
= 0.25V
1
EE
Figure 5 illustrates the overload
pp
. When the load is tied to V
Frequency (MHz)
Time (50ns/div)
Channel B
The layout of Comlinear’s
10
Output
Input
CC
Channel A
- V
Input referred
EE
= 10V, but
Channel
EE
, the
5
Driving Cables and Capacitive Loads
When driving cables, double termination is used to
prevent reflections. For capacitive load applications, a
small series resistor at the output of the CLC427 will
improve stability.
Capacitive Load
section, gives the recommended series resistance value
for optimum flatness at various capacitive loads.
Power Dissipation
The power dissipation of an amplifier can be described in
two conditions:
The following steps can be taken to determine the power
consumption for each CLC427 amplifier:
Add the total RMS powers for both channels to determine
the power dissipated by the dual.
Figure 7: Input Referred Crosstalk vs. Frequency
• Quiescent Power Dissipation -
• Total Power Dissipation -
1. Determine the quiescent power
2. Determine the RMS power at the output stage
3. Determine the total RMS power
P
P
P
P
P
-100
Q
T
-40
-50
-60
-70
-80
-90
Q
O
T
(with Load Condition)
(No Load Condition)
= P
= I
= (V
1
Figure 8: Pulsed crosstalk
CC
Q
CC
+ P
(V
– V
CC
O
The Frequency Response vs.
plot, in the typical performance
Frequency (MHz)
Time (50ns/div)
load
– V
Channel A
Channel B
) (I
EE
10
load
)
)
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