CLC5602IM datasheet(8/12 Pages) NSC

8 / 12 page

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Feedback Resistor Selection

The feedback resistor, Rf, affects the loop gain and

frequency response of a current feedback amplifier.

Optimum performance of the CLC5602, at a gain of

+2V/V, is achieved with Rf equal to 750Ω. The frequency

response plots in the

Typical Performance sections

illustrate the recommended Rf for several gains. These

recommended values of Rf provide the maximum band-

width with minimal peaking.

Within limits, Rf can be

adjusted to optimize the frequency response.

Decrease Rf to peak frequency response and

extend bandwidth

Increase Rf to roll off frequency response and

compress bandwidth

As a rule of thumb, if the recommended Rf is doubled,

then the bandwidth will be cut in half.

Unity Gain Operation

The recommended Rf for unity gain (+1V/V) operation

is 1k

Ω.R

g is left open.

Parasitic capacitance at the

inverting node may require a slight increase in Rf to

maintain a flat frequency response.

Load Termination

The CLC5602 can source and sink near equal amounts

of current. For optimum performance, the load should be

tied to Vcm.

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 CLC5602 will

improve

stability

and

settling

performance. The

Frequency Response vs. CL plot, shown below in

Figure 7, gives the recommended series resistance value

for optimum flatness at various capacitive loads.

Figure 7: Frequency Response vs. CL

Transmission Line Matching

One method for matching the characteristic impedance

(Zo) of a transmission line or cable is to place the

appropriate resistor at the input or output of the amplifier.

Figure 8 shows typical inverting and non-inverting circuit

configurations for matching transmission lines.

Non-inverting gain applications:

Connect Rg directly to ground.

Make R1, R2, R6, and R7 equal to Zo.

Use R3 to isolate the amplifier from reactive

loading caused by the transmission line,

or by parasitics.

Figure 8: Transmission Line Matching

Inverting gain applications:

Connect R3 directly to ground.

Make the resistors R4, R6, and R7 equal to Zo.

Make R5 II Rg = Zo.

The input and output matching resistors attenuate the

signal by a factor of 2, therefore additional gain is needed.

Use C6 to match the output transmission line over a

greater frequency range. C6 compensates for the increase

of the amplifier’s output impedance with frequency.

Power Dissipation

Follow these steps to determine the power consumption

of the CLC5602:

1. Calculate the quiescent (no-load) power:

Pamp = ICC (VCC - VEE)

2. Calculate the RMS power at the output stage:

Po = (VCC - Vload) (Iload), where Vload and Iload

are the RMS voltage and current across the

external load.

3. Calculate the total RMS power:

Pt = Pamp + Po

The maximum power that the DIP and SOIC packages

can dissipate at a given temperature is illustrated in

Figure 9. The power derating curve for any CLC5602

package can be derived by utilizing the following

equation:

where

Tamb = Ambient temperature (°C)

JA = Thermal resistance, from junction to ambient,

for a given package (°C/W)

V2 +-

1/2

CLC5602

(175

Tamb

°−

)

Frequency (Hz)

10M

100M

Vo = 1Vpp

CL = 10pF

Rs = 46.4Ω

CL = 100pF

Rs = 20Ω

CL = 1000pF

Rs = 6.7Ω

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