MAX477 Maxim, MAX477 Datasheet - Page 7

• Manufacturer Part Number: MAX477
• Description: 300MHz High-Speed Op Amp
• Manufacturer: Maxim

The MAX477 allows the flexibility and ease of a classic
voltage-feedback architecture while maintaining the
high-speed benefits of current-mode feedback (CMF)
amplifiers. Although the MAX477 is a voltage-feedback
op amp, its internal architecture provides an 1100V/µs
slew rate and a low 8mA supply current. CMF ampli-
fiers offer high slew rates while maintaining low supply
current, but use the feedback and load resistors as part
of the amplifier’s frequency compensation network. In
addition, they have only one input with high imped-
ance.
The MAX477 has speed and power specifications like
those of current-feedback amplifiers, but has high input
impedance at both input terminals. Like other voltage-
feedback op amps, its frequency compensation is
independent of the feedback and load resistors, and it
exhibits a constant gain-bandwidth product. However,
unlike standard voltage-feedback amplifiers, its large-
signal slew rate is not limited by an internal current
source, so the MAX477 exhibits a very high full-power
bandwidth.
_____________________Pin Description
Figure 1a. Inverting Gain Configuration
_______________Detailed Description
SO/µMAX/DIP
1, 5, 8
PIN
2
3
4
6
7
V
V
OUT
IN
= -(R
F
/R
R
G
G
) V
SOT23
_______________________________________________________________________________________
IN
—
4
3
2
1
5
NAME
MAX477
OUT
N.C.
V
IN+
V
IN-
CC
EE
R
F
No Connect. Not inter-
nally connected.
Inverting Input
Noninverting Input
Negative Power
Supply
Amplifier Output
Positive Power
Supply
FUNCTION
V
OUT
300MHz High-Speed Op Amp
Under short-circuit conditions, the output current is typi-
cally limited to 150mA. This is low enough that a short to
ground of any duration will not cause permanent dam-
age to the chip. However, a short to either supply will
significantly increase the power dissipation and may
cause permanent damage. The high output-
current capability is an advantage in systems that trans-
mit a signal to several loads. See High-Performance
Video Distribution Amplifier in the Applications
Information section.
To obtain the MAX477’s full 300MHz bandwidth, Micro-
strip and Stripline techniques are recommended in
most cases. To ensure the PC board does not degrade
the amplifier’s performance, design the board for a fre-
quency greater than 1GHz. Even with very short traces,
use these techniques at critical points, such as inputs
and outputs. Whether you use a constant-impedance
board or not, observe the following guidelines when
designing the board:
Figure 1b. Noninverting Gain Configuration
__________Applications Information
Do not use wire-wrap boards. They are too inductive.
Do not use IC sockets. They increase parasitic
capacitance and inductance.
In general, surface-mount components have shorter
leads and lower parasitic reactance, giving better
high-frequency performance than through-hole com-
ponents.
The PC board should have at least two layers, with
one side a signal layer and the other a ground plane.
Keep signal lines as short and straight as possible.
Do not make 90° turns; round all corners.
The ground plane should be as free from voids as
possible.
V
OUT
= [1 + (R
Output Short-Circuit Protection
R
G
F
/R
G
V
)] V
IN
IN
Grounding, Bypassing,
MAX477
and PC Board Layout
R
F
V
OUT
7