CLC450 datasheet(10/12 Pages) NSC

10 / 12 page

http://www.national.com

Rt - Optional resistor for inverting gain configura-

tions (Select Rt to yield desired input impedance

= Rg || Rt)

C1, C2 - 0.1µF ceramic capacitors

C3, C4 - 6.8µF tantalum capacitors

Components not used:

C5, C6, C7, C8

R1 thru R8

The evaluation boards are designed to accommodate

dual supplies. The boards can be modified to provide

single supply operation.

For best performance; 1) do

not connect the unused supply, 2) ground the unused

supply pin.

SPICE Models

SPICE models provide a means to evaluate amplifier

designs. Free SPICE models are available for National’s

monolithic amplifiers that:

Support Berkeley SPICE 2G and its many derivatives

Reproduce typical DC, AC, Transient, and Noise

performance

Support room temperature simulations

The

readme file that accompanies the diskette lists

released models, and provides a list of modeled parame-

ters.

The application note OA-18, Simulation SPICE

Models for National’s Op Amps, contains schematics and

a reproduction of the readme file.

Single Supply Cable Driver

The typical application shown on the front page shows

the CLC450 driving 10m of 75

Ω coaxial cable. The

CLC450 is set for a gain of +2V/V to compensate for the

divide-by-two voltage drop at Vo.

Single Supply Lowpass Filter

Figures 9 and 10 illustrate a lowpass filter and design

equations. The circuit operates from a single supply of

+5V. The voltage divider biases the non-inverting input to

2.5V. And the input is AC coupled to prevent the need for

level shifting the input signal at the source.

Use the

design equations to determine R1, R2, C1, and C2 based

on the desired Q and corner frequency.

Figure 9: Lowpass Filter Topology

Figure 10: Design Equations

This example illustrates a lowpass filter with Q = 0.707

and corner frequency fc = 10MHz. A Q of 0.707 was cho-

sen to achieve a maximally flat, Butterworth response.

Figure 11 indicates the filter response.

Figure 11: Lowpass Response

Twisted Pair Driver

The high output current and low distortion, of the

CLC450, make it well suited for driving transformers.

Figure 12 illustrates a typical twisted pair driver utilizing

the CLC450 and a transformer. The transformer

provides the signal and its inversion for the twisted pair.

Figure 12: Twisted Pair Driver

To match the line’s characteristic impedance (Zo) set:

RL = Zo

Rm = Req

Application Circuits

Ω

0.1

µF

Vin

Ω

0.1

µF

0.1

µF

Ω

CLC450

+5V

0.1

µF

100

Ω

1.698k

Ω

158

Ω

158

Ω

100pF

Gain

Corner frequency

RR C C

(1 K)

For R

R and C

(3 K)

12 1 2

== +

−

Frequency (Hz)

-21

-15

-9

-3

10M

100M

Vin

UTP

Req

I:n

V = Av Vin

CLC450

v in

-n

v in

ov in

CLC450 Datasheet(PDF) 10 Page - National Semiconductor (TI)

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