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CLC5665IN Schematic ( PDF Datasheet ) - National Semiconductor

Teilenummer CLC5665IN
Beschreibung Low Distortion Amplifier with Disable
Hersteller National Semiconductor
Logo National Semiconductor Logo 




Gesamt 8 Seiten
CLC5665IN Datasheet, Funktion
N
CLC5665
Low Distortion Amplifier with Disable
June 1999
General Description
The CLC5665 is a low-cost, wideband amplifier that provides very
low 2nd and 3rd harmonic distortion at 1MHz (-89/-92dBc). The
great slew rate of 1800V/µs, bandwidth of 90MHz (Av = +1) and
fast disable make it an excellent choice for many high speed
multiplexing applications. Like all current feedback op amps, the
CLC5665 allows the frequency response to be optimized
(or adjusted) by the selection of the feedback resistor. For
demanding video applications, the 0.1dB bandwidth to 20MHz
and differential gain/phase of 0.05%/0.05° make the CLC5665
the preferred component for broadcast quality NTSC and PAL
video systems.
The large voltage swing (28Vpp), continuous output current
(85mA) and slew rate (1800V/µs) provide high-fidelity signal
conditioning for applications such as CCDs, transmission lines
and low impedance circuits.
xDSL, video distribution, multimedia and general purpose
applications will benefit from the CLC5665’s wide bandwidth and
disable feature. Power is reduced and the output becomes a high
impedance when disabled. The wide gain range of the CLC5665
makes this general purpose op amp an improved solution for
circuits such as active filters, single-to-differential-ended drivers,
DAC transimpedance amplifiers and MOSFET drivers.
Features
s 0.1dB gain flatness to 20MHz (Av = +2)
s 90MHz bandwidth (Av = +1)
s Large signal BW 25MHz
s 1800V/µs slew rate
s 0.05%/0.05° differential gain/phase
s ±5V, ±15V or single supplies
s 200ns disable to high-impedance output
s Wide gain range
s -89/-92dBc HD2/HD3 (RL = 500Ω)
s Low cost
Applications
s xDSL driver
s Twisted pair driver
s Cable driver
s Video distribution
s CCD clock driver
s Multimedia systems
s DAC output buffers
s Imaging systems
Non-Inverting Frequency Response
Gain
Av = 1
Rf = 698
Phase
Av = 50
Av = 10
Rf = 100 Av = 2
Rf = 604
Av = 1
Av = 50
Rf = 500
Av = 2
Av = 10
0
-45
-90
-135
-180
1 10 100
Frequency (MHz)
+
Vin (Vpp)
-
DIS
+
CLC5665
-
Rf1
Rg 604
1.2k
Rf2
604
-
CLC5665
+
Typical Application
Differential Line Driver for xDSL
Ro
Vo = 2Vin
1:n
nVo
RL
Ro
Note: Supply and Bypassing not shown.
DIS
© 1999 National Semiconductor Corporation
Printed in the U.S.A.
Pinout
DIP & SOIC
NC 1
Vinv 2
Vnon-inv 3
-Vcc 4
-
+
8 DIS
7 +Vcc
6 Vout
5 NC
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CLC5665IN Datasheet, Funktion
Set up the CLC5665 as a difference amplifier. Vd is
determined by:
Vd
Vin
=
2
1+
RRgf11
= 2 Rf2
Rg2
Make the best use of the CLC5665’s output drive
capability as follows:
Rm
+ Req
=
2 Vmax
Imax
where Req is the transformed value of the load imped-
ance, Vmax is the Output Voltage Range, and Imax is the
maximum Output Current.
Match the line’s characteristic impedance:
RL = Zo
Rm = Req
n = RL
Req
Select the transformer so that it loads the line with a
value very near Zo over frequency range. The output
impedance of the CLC5665 also affects the match. With
an ideal transformer we obtain:
Return Loss = −20 log10
n2 Zo(5665)(jω)
Zo
, dB
where Zo(5665)(jω) is the output impedance of the
CLC5665 and |Zo(5665)(jω)| << Rm.
The load voltage and current will fall in the ranges:
Vo n Vmax
Io
Imax
n
The CLC5665’s high output drive current and low
distortion make it a good choice for this application.
Full Duplex Cable Driver
The circuit shown in Figure 8 below, operates as a full
duplex cable driver which allows simultaneous transmis-
sion and reception of signals on one transmission line.
The circuit on either side of the transmission line uses are
CLC5665 as a cable driver, and the second CLC5665 as
a receiver. VoA is an attenuated version of VinA, while VoB
is an attenuated version of VinB.
VinA
Rt1
VoB
+
CLC5665
-
Rm1
Rf1 Rg2
Rf2
-
CLC5665
+
Rt2
Z0
Rm1
+
CLC5665
-
Rg2 Rf1
Rf2
-
Rt2 CLC5665
+
VinB
Rt1
VoA
Figure 8: Full Duplex Cable Driver
Rm1 is used to match the transmission line. Rf2 and Rg2
set the DC gain of the CLC5665, which is used in a
difference mode. Rt2 provides good CMRR and DC
offset. The transmitting CLC5665’s are shown in a unity
gain configuration because they consume the least
power of any gain, for a given load. For proper operation
we need Rf2 = Rg2.
The receiver output voltages are:
VoutA(B)
VinA(B) A
+
VinB(A)
2
1
Rf2
Rg2
+
Zo(5665)(jω)
Rm1 
where A is the attenuation of the cable, Zo(5665)(jω) is
the output impedance of the CLC5665, and |Zo(5665)(jω)|
<< Rm1.
We selected the component values as follows:
s Rf1 = 1.2k, the recommended value for
CLC5665 at unity gain
s Rm1 = Zo = 50, the characteristic impedance
of the transmission line
s Rf2 = Rg2 = 750Rm1, the recommended
value for the CLC5665 at Av = 2
s
Rt2
=
(Rf2
|| Rg2 )
Rm1
2
=
25
These values give excellent isolation from the other input:
VoA(B) ≈ −38dB, f = 5.0MHz
VinB(A)
The CLC5665 provides large output current drive, while
consuming little supply current, at the nominal bias point.
It also produces low distortion with large signal swings
and heavy loads. These features make the CLC5665 an
excellent choice for driving transmission lines.
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