clc453 National Semiconductor Corporation, clc453 Datasheet - Page 7

• Manufacturer Part Number: clc453
• Description: Single Supply, Low-power, High Output, Programmable Buffer
• Manufacturer: National Semiconductor Corporation

The CLC453 is a current feedback buffer built in an
advanced complementary bipolar process. The CLC453
operates from a single 5V supply or dual ±5V supplies.
Operating from a single 5V supply, the CLC453 has the
following features:
The CLC453 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
CLC452 can be used. The CLC452 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:
Closed Loop Gain Selection
The CLC453 is a current feedback op amp with
R
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 CLC453 is excellent and
stable over temperature change.
setting resistors, R
with a process variation of ± 20% and a temperature
coefficient of ˜ 2000ppm/°C.
values change with processing and temperature, their
ratio (R
used in series with R
will suffer.
f
= R
+1V/V
+2V/V
-1V/V
Gain
A
g
Gains of +1, -1, and 2V/V are achievable without
external resistors
Provides 100mA of output current while
consuming only 15mW of power
Offers low -65/-84dBc 2nd and 3rd harmonic
distortion
Provides BW > 80MHz and 1MHz distortion
< -70dBc at V
Independence of AC bandwidth and voltage gain
Inherently stable at unity gain
Adjustable frequency response with feedback resistor
High slew rate
Fast settling
v
f
/R
= 1k
g
) remains constant. If an external resistor is
Non-Inverting (pin3)
on chip (in the package). Select from
input signal
input signal
f
and R
ground
o
g
, gain accuracy over temperature
= 2V
Input Connections
g
pp
are diffused silicon resistors
Although their absolute
CLC453 Design Information
Inverting (pin2)
The internal gain
input signal
NC (open)
ground
CLC453 Operation
7
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.
where:
The denominator of Equation 1 is approximately equal to
1 at low frequencies. Near the -3dB corner frequency,
the interaction between R
performance. The value of the feedback resistor has a
large affect on the circuits performance. Increasing R
has the following affects:
Single Supply Operation (V
The specifications given in the +5V Electrical Character-
istics table for single supply operation are measured
with a common mode voltage (V
voltage 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 CLC453 is typically +0.8V to
+4.2V. The typical output range with R
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.
V
V
in
o
A
R
Z(j ) is the CLC453’s open loop transimpedance
gain
Decreases loop gain
Decreases bandwidth
Reduces gain peaking
Lowers pulse response overshoot
Affects frequency response phase linearity
Z j
v
f
R
1
is the feedback resistor
is the closed loop DC voltage gain
f
A
Z(j )
R
v
is the loop gain
f
Equation 1
f
and Z(j ) dominates the circuit
CC
= +5V, V
cm
) of 2.5V. V
L
http://www.national.com
=100
EE
= GND)
cm
is +1.0V
is the
f