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CLC428AJE Schematic ( PDF Datasheet ) - National Semiconductor

Teilenummer CLC428AJE
Beschreibung Dual Wideband/ Low-Noise/ Voltage Feedback Op Amp
Hersteller National Semiconductor
Logo National Semiconductor Logo 




Gesamt 8 Seiten
CLC428AJE Datasheet, Funktion
N
June 1999
CLC428
Dual Wideband, Low-Noise, Voltage Feedback Op Amp
General Description
The CLC428 is a very high-speed dual op amp that offers a traditional
voltage-feedback topology featuring unity-gain stability and slew-
enhanced circuitry. The CLC428’s ultra low noise and very low
harmonic distortion combine to form a very wide dynamic-range op
amp that operates from a single (5 to 12V) or dual (±5V) power supply.
Each of the CLC428’s closely matched channels provides a 160MHz
unity-gain bandwidth with an ultra low input voltage noise density
(2nV/Hz). Very low 2nd/3rd harmonic distortion (-62/-72dBc) as well
as high channel-to-channel isolation (-62dB) make the CLC428 a
perfect wide dynamic-range amplifier for matched I/Q channels.
With its fast and accurate settling (16ns to 0.1%), the CLC428 is also
a excellent choice for wide-dynamic range, anti-aliasing filters
to buffer the inputs of hi-resolution analog-to-digital converters.
Combining the CLC428’s two tightly-matched amplifiers in a single
eight-pin SOIC reduces cost and board space for many composite
amplifier applications such as active filters, differential line drivers/
receivers, fast peak detectors and instrumentation amplifiers.
Features
s Wide unity-gain bandwidth: 160MHz
s Ultra-low noise: 2.0nV/Hz
s Low distortion: -78dBc 2nd (2MHz)
-62/-72dBc (10MHz)
s Settling time: 16ns to 0.1%
s Supply voltage range: ±2.5 to ±5 or
single supply
s High output current: ±80mA
Applications
s General purpose dual op amp
s Low noise integrators
s Low noise active filters
s Diff-in/diff-out instrumentation amp
s Driver/receiver for transmission systems
s High-speed detectors
s I/Q channel amplifiers
To reduce design times and assist in board layout, the CLC428 is
supported by an evaluation board and a SPICE simulation model
available from National Semiconductor.
Typical Application
5-Decade Integrator
© 1999 National Semiconductor Corporation
Printed in the U.S.A.
Pinout
DIP & SOIC
Vout1 1
Vinv1 2
Vnon-inv1 3
-Vcc 4
-
+
-
+
8 +Vcc
7 Vout2
6 Vinv2
5 Vnon-inv2
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CLC428AJE Datasheet, Funktion
The maximum speed of detection is limited by the delay
of the op amps and the diodes. The use of Schottky diodes
will provide faster response.
Adjustable or Bandpass Equalizer
A "boost" equalizer can be made with the CLC428 by
summing a bandpass response with the input signal, as
shown in Figure 9.
Figure 6
Positive Peak Detector
The CLC428's dual amplifiers can be used to implement a
unity-gain peak detector circuit as shown in Figure 7.
Q1
Figure 9
The overall transfer function is shown in Eq. 5.
FHG c hIJVout =
Rb
KVin K Ra + Rb
s2
s2Qωo
+
s ωo
Q
+
ω
2
o
1
Eq. 5
To build a boost circuit, use the design equations Eq. 6 and
Eq. 7.
Figure 7
The acquisition speed of this circuit is limited by the
dynamic resistance of the diode when charging Chold. A
plot of the of the circuit's performance is shown in Figure
8 with a 1MHz sinusoidal input.
c hR2C = Q ,
2 ωo
2C Ra||Rb
=1
Qω o
Eq. 6,7
Select R2 and C using Eq. 6. Use reasonable values for
high frequency circuits - R2 between 10and 5k, C
between 10pF and 2000pF. Use Eq. 7 to determine the
parallel combination of Ra and Rb. Select Ra and Rb by
either the 10to 5kcriteria or by other requirements
based on the impedance Vin is capable of driving. Finish
the design by determining the value of K from Eq. 8.
c hPeak Gain = Vout
Vin
ωo
= R2 1
2KRa
Eq. 8
Figure 10 shows an example of the response of the circuit
of Figure 9, where fo is 2.3MHz. The component values
are as follows: Ra =2.1k, Rb =68.5, R2 =4.22k, R
=500, KR =50, C =120pF.
Figure 8
A current source, built around Q1, provides the necessary
bias current for the second amplifier and prevents satura-
tion when power is applied. The resistor, R, closes the loop
while diode D2 prevents negative saturation when Vin is
less than Vc. A MOS-type switch (not shown) can be used
to reset the capacitor's voltage.
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6
Figure 10

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