CLC450 datasheet(7/12 Pages) NSC

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CLC450 OPERATION

The CLC450 is a current feedback amplifier built in an

advanced complementary bipolar process. The CLC450

operates from a single 5V supply or dual ±5V supplies.

Operating from a single supply, the CLC450 has the

following features:

Provides 100mA of output current while

consuming 7.5mW of power

Offers low -79/-75dB 2nd and 3rd harmonic

distortion

Provides BW > 60MHz and 1MHz distortion

< -65dBc at Vo = 2.5Vpp

The CLC450 performance is further enhanced in ±5V

supply applications as indicated in the

±5V Electrical

Characteristics table and ±5V Typical Performance plots.

Current Feedback Amplifiers

Some of the key features of current feedback technology

are:

Independence of AC bandwidth and voltage gain

Inherently stable at unity gain

Adjustable frequency response with feedback resistor

High slew rate

Fast settling

Current feedback operation can be described using a simple

equation. The voltage gain for a non-inverting or inverting

current feedback amplifier is approximated by Equation 1.

Equation 1

where:

Av is the closed loop DC voltage gain

Rf is the feedback resistor

Z(j

ω) is the CLC450’s open loop transimpedance

gain

is the loop gain

The denominator of Equation 1 is approximately equal to

1 at low frequencies. Near the -3dB corner frequency, the

interaction between Rf and Z(jω) dominates the circuit

performance. The value of the feedback resistor has a

large affect on the circuits performance. Increasing Rf

has the following affects:

Decreases loop gain

Decreases bandwidth

Reduces gain peaking

Lowers pulse response overshoot

Affects frequency response phase linearity

Refer to the

Feedback Resistor Selection section for

more details on selecting a feedback resistor value.

Z(j )

()

CLC450 DESIGN INFORMATION

Single Supply Operation (VCC = +5V, VEE = GND)

The specifications given in the

+5V Electrical Character-

istics table for single supply operation are measured with

a common mode voltage (Vcm) of 2.5V. Vcm is the volt-

age around which the inputs are applied and the

output voltages are specified.

Operating from a single +5V supply, the Common Mode

Input Range (CMIR) of the CLC450 is typically +0.8V to

+4.2V. The typical output range with RL=100Ω is +1.0V

to +4.0V.

For single supply DC coupled operation, keep input

signal levels above 0.8V DC. For input signals that drop

below 0.8V DC, AC coupling and level shifting the signal

are recommended. The non-inverting and inverting

configurations for both input conditions are illustrated in

the following 2 sections.

DC Coupled Single Supply Operation

Figures 1 and 2 show the recommended non-inverting

and inverting configurations for input signals that remain

above 0.8V DC.

CLC450

0.1

µF

6.8

µF

Vin

== +

Vcm

VCC

Vcm

Note: Rt, RL and Rg are tied

to Vcm for minimum power

consumption and maximum

output swing.

Vcm

0.1

µF

6.8

µF

Vin

== −

CLC450

Vcm

VCC

Vcm

Note: Rb, provides DC bias

for non-inverting input.

Rb, RL and Rt are tied

to Vcm for minimum power

consumption and maximum

output swing.

Vcm

Select Rt to yield

desired Rin = Rt || Rg

Figure 1: Non-Inverting Configuration

Figure 2: Inverting Configuration

CLC450 Datasheet(PDF) 7 Page - National Semiconductor (TI)

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