clc522 National Semiconductor Corporation, clc522 Datasheet - Page 10

• Manufacturer Part Number: clc522
• Description: Wideband Variable-gain Amplifier
• Manufacturer: National Semiconductor Corporation

www.national.com
Application Division
Further discussion and plots of noise and the noise model is
provided in Application Note OA-23. National also provides
SPICE models that model internal noise and other param-
eters for a typical part.
Circuit Layout Considerations
Please refer to the CLC522 Evaluation Board literature for
precise layout guidelines. Good high-frequency operation
requires all of the de-coupling capacitors shown in to be
placed as close as possible to the power supply pins in order
to insure a proper high-frequency low-impedance bypass.
Adequate ground plane and low-inductive power returns are
also required of the layout. Minimizing the parasitic capaci-
tances at pins 3, 4, 5, 6, 9, 10 and 12 as shown in Figure 7
will assure best high frequency performance.
FIGURE 5. Input referred Voltage Noise vs. A
FIGURE 6.
(Continued)
DS012718-38
DS012718-39
V max
(7)
10
Vref (pin 9) to ground should include a small resistor value of
25 ohms or greater to buffer the internal voltage follower. The
parasitic inductance of component leads or traces to pins 4,
5 and 9 should also be kept to a minimum. Parasitic or load
capacitance, C
margin and can lead to frequency response peaking or
circuit oscillation. This should be treated with a small series
resistor between output (pin 10) and C
Time vs. Capacitive Load for a recommended series resis-
tance).
Component parasitics also influence high frequency results,
therefore it is recommended to use metal film resistors such
as RN55D or leadless components such as surface mount
devices. High profile sockets are not recommended. If sock-
eting is necessary, it is recommended to use low impedance
flush mount connector jacks such as Cambion (P/N 450-
2598).
Application Circuits
Four-Quadrant Multiplier
Applications requiring multiplication, squaring or other
non-linear functions can be implemented with four-quadrant
multipliers. The CLC522 implements a four-quadrant multi-
plier as illustrated in Figure 8 .
L
, on the output (pin 10) degrades phase
FIGURE 7.
FIGURE 8.
L
(see the plot Settling
DS012718-41
DS012718-40