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CLC451 Operation

The CLC451 is a current feedback buffer built in an

advanced complementary bipolar process. The CLC451

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

Operating from a single 5V supply, the CLC451 has the

following features:

s

Gains of +1, -1, and 2V/V are achievable without

external resistors

s

Provides 100mA of output current while

consuming only 7.5mW of power

s

Offers low -66/-75dBc 2nd and 3rd harmonic

distortion

s

Provides BW > 60MHz and 1MHz distortion

The CLC451 performance is further enhanced in ±5V

supply applications as indicated in the

±5V Electrical

Characteristics table and ±5V Typical Performance plots.

If gains other than +1, -1, or +2V/V are required, then the

CLC450 can be used. The CLC450 is a current feedback

amplifier with near identical performance and allows for

external feedback and gain setting resistors.

Current Feedback Amplifiers

Some of the key features of current feedback technology are:

s

Independence of AC bandwidth and voltage gain

s

Inherently stable at unity gain

s

Adjustable frequency response with feedback resistor

s

High slew rate

s

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:

s

s

s

Z(j

ω) is the CLC451’s open loop transimpedance

gain

s

is the loop gain

The denominator of Equation 1 is approximately equal to

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

performance. The value of the feedback resistor has a

has the following affects:

s

Decreases loop gain

s

Decreases bandwidth

s

Reduces gain peaking

s

Lowers pulse response overshoot

s

Affects frequency response phase linearity

V

V

A

1

R

Z(j )

o

in

v

f

=

+

ω

Zj

ω

()

CLC451 Design Information

Closed Loop Gain Selection

The CLC451 is a current feedback op amp with

three closed loop gains without using any external gain or

feedback resistors. Implement gains of +2, +1, and

-1V/V by connecting pins 2 and 3 as described in the

chart below.

The gain accuracy of the CLC451 is excellent and

stable over temperature change.

The internal gain

with a process variation of ± 20% and a temperature

coefficient of ˜ 2000ppm/°C. Although their absolute

values change with processing and temperature, their

will suffer.

The specifications given in the

+5V Electrical Character-

istics table for single supply operation are measured with

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 CLC451 is typically +0.8V to

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, 2, and 3 on the following page, show the

recommended configurations for input signals that

remain above 0.8V DC.

Gain

Input Connections

Non-Inverting (pin3)

Inverting (pin2)

-1V/V

ground

input signal

+1V/V

input signal

NC (open)

+2V/V

input signal

ground