clc449 National Semiconductor Corporation, clc449 Datasheet - Page 12

• Manufacturer Part Number: clc449
• Description: 1.1ghz Ultra-wideband Monolithic Op Amp
• Manufacturer: National Semiconductor Corporation

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Application Division
The noise of a simple input matching resistor connected to
ground can be calculated by setting G to 0 in this equation.
Thus, this circuit reduces the thermal noise power produced
by the matching resistor by a factor of (1+G).
Rectifier Circuit
Wide bandwidth rectifier circuits have many applications.
Figure 10 shows a 200MHz wideband full-wave rectifier
circuit using a CLC449 and a CLC522 amplifier. Schottky or
PIN diodes are used for D
half-wave rectifier whose signals are taken at the feedback
diode connection. The CLC522 takes the difference of the
two half-wave rectified signals, producing a full-wave
rectifier. The CLC522 is used at a gain of 5 to achieve high
differential bandwidth. For best high frequency performance,
maintain low parasitic capacitance from the diodes D
D
2
to ground, and from the input of the CLC522 to ground.
e
2
R
f
4 TR
k
s
R
1
in
and D
R
1 G
s
2
. They produce an active
(Continued)
1
and
12
Flash A/D Application
The Typical Application circuit on the front page shows the
CLC449 driving a flash A/D. Flash A/D’s require fast settling,
low distortion, low noise and wide bandwidth to achieve high
Effective Number of Bits and Spurious Free Dynamic Range
(SFDR).
This circuit connects a CLC449 to a TDA8716, 8-bit,
120MHz Flash Converter. The input capacitance for this
converter is typically 13pF plus layout capacitace. From the
R
Performance Characteristics section, select a series
resistor (R
CLC449 to achieve settling to 0.1% in approximately 11ns.
Keep the amplifier noise seen at the A/D input at least 3dB
lower than the A/D’s noise, to avoid degrading A/D noise
performace.
s
and Settling Time vs. C
s
) of 55 . Place R
FIGURE 10. Full-Wave Rectifier
s
in series with the output of the
L
plot in the Typical
DS012715-44