CLC427 datasheet(5/8 Pages) NSC

5 / 8 page

http://www.national.com

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 VEE. When the load is tied to VEE, the

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.

Figure 5 illustrates the overload

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, VCC - VEE = 10V, but

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.

Figure 5: Overdrive Recovery

Channel Matching

Channel matching and crosstalk rejection are largely

dependent on board layout.

The layout of Comlinear’s

dual amplifier evaluation boards are designed to produce

optimum channel matching and isolation.

Channel

matching for the CLC427 is shown in Figure 6.

Figure 6: Channel Matching

The CLC427’s channel-to-channel isolation is better than

-70dB for video frequencies of 4MHz.

Input referred

crosstalk vs frequency is illustrated in Figure 7. Pulsed

crosstalk is shown in Figure 8.

Figure 7: Input Referred Crosstalk vs. Frequency

Figure 8: Pulsed crosstalk

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.

The

Frequency Response vs.

Capacitive Load

plot, in the typical performance

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:

• Quiescent Power Dissipation -

PQ (No Load Condition)

• Total Power Dissipation -

PT (with Load Condition)

The following steps can be taken to determine the power

consumption for each CLC427 amplifier:

1. Determine the quiescent power

PQ = ICC (VCC – VEE)

2. Determine the RMS power at the output stage

PO = (VCC – Vload) (Iload)

3. Determine the total RMS power

PT = PQ + PO

Add the total RMS powers for both channels to determine

the power dissipated by the dual.

Time (50ns/div)

Input

Output

Frequency (MHz)

Channel A

Channel B

Vout = 0.25Vpp

110

Frequency (MHz)

100

-100

-90

-80

-70

-60

-50

-40

Time (50ns/div)

Channel A

Channel B

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