CLC450 datasheet(8/12 Pages) NSC

8 / 12 page

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AC Coupled Single Supply Operation

Figures 3 and 4 show possible non-inverting and invert-

ing configurations for input signals that go below 0.8V

DC. The input is AC coupled to prevent the need for

level shifting the input signal at the source. The resistive

voltage divider biases the non-inverting input to VCC ÷2

= 2.5V (For VCC = +5V).

Figure 3: AC Coupled Non-Inverting Configuration

Figure 4: AC Coupled Inverting Configuration

Dual Supply Operation

The CLC450 operates on dual supplies as well as single

supplies. The non-inverting and inverting configurations

are shown in Figures 5 and 6.

Figure 5: Dual Supply Non-Inverting Configuration

Figure 6: Dual Supply Inverting Configuration

Feedback Resistor Selection

The feedback resistor, Rf, affects the loop gain and

frequency response of a current feedback amplifier.

Optimum performance of the CLC450, at a gain of +2V/V,

is achieved with Rf equal to 1kΩ. The frequency response

plots

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 1.5k

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.

Bandwidth vs. Output Amplitude

The bandwidth of the CLC450 is at a maximum for

output voltages near 1Vpp. The bandwidth decreases

for smaller and larger output amplitudes. Refer to the

Frequency Response vs. Vo plots.

Load Termination

The CLC450 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 CLC450 will

improve

stability

and

settling

performance. The

Frequency Response vs. CL and Recommended Rs

vs. CL plots, in the typical performance section, give the

recommended series resistance value for optimum

flatness at various capacitive loads.

0.1

µF

6.8

µF

Vin

2.5











 +

low frequency cutoff

2R C

, where: R

RRsource

CLC450

VCC

0.1

µF

6.8

µF

Vin

2.5

=−











 +

low frequency cutoff

2R C

CLC450

VCC

CLC450

0.1

µF

6.8

µF

Vin

VCC

0.1

µF

6.8

µF

VEE

CLC450

0.1

µF

6.8

µF

Vin

VCC

0.1

µF

6.8

µF

VEE

Note: Rb provides DC bias

for the non-inverting input.

Select Rt to yield desired

Rin = Rt || Rg.

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