Hig h -S p e e d , Lo w -P o w e r, S in g le -S u p p ly,
Mu lt ic h a n n e l, Vid e o Mu lt ip le x e r-Am p lifie rs
output swings from 30mV above V to within 730mV of
EE
_______________De t a ile d De s c rip t io n
the supply rail. Local feedback around the output stage
ensures low open-loop output impedance to reduce
gain sensitivity to load variations. This feedback also
produces demand-driven bias current to the output
transistors for ±95mA drive capability while constrain-
ing total supply current to only 6.1mA.
The MAX4310/MAX4311/MAX4312 combine 2-channel,
4-channel, or 8-channel multiplexers, respectively, with
a n a d jus ta b le -g a in outp ut a mp lifie r op timize d for
c los e d -loop g a ins of + 1V/V (0d B) or g re a te r. The
MAX4313/MAX4314/MAX4315 combine 2-channel, 4-
channel, or 8-channel multiplexers, respectively, with a
+2V/V (6dB) fixed-gain amplifier, optimized for driving
back-terminated cables. These devices operate from a
single supply voltage of +4V to +10.5V, or from dual
supplies of ±2V to ±5.25V. The outputs may be placed
in a high-impedance state and the supply current mini-
mized by forcing the SHDN pin low. The input multi-
plexers feature short 40ns channel-switching times and
small 10mVp-p switching transients. The input capaci-
tance remains constant at 1pF whether the channel is
on or off, providing a predictable input impedance to
the signal source. These devices feature single-supply,
ra il-to-ra il, volta g e -fe e d b a c k outp ut a mp lifie rs tha t
achieve up to 540V/µs slew rates and up to 345MHz -3dB
bandwidths. These devices also feature excellent har-
monic distortion and differential gain/phase perfor-
mance.
Fe e d b a c k a n d Ga in Re s is t o r S e le c t io n
(MAX4 3 1 0 /MAX4 3 1 1 /MAX4 3 1 2 )
Select the MAX4310/MAX4311/MAX4312 gain-setting
feedback (R ) and input (R ) resistors to fit your applica-
F
G
tion. Large resistor values increase voltage noise and
interact with the amplifier’s input and PC board capaci-
tance. This can generate undesirable poles and zeros,
and can decrease bandwidth or cause oscillations. For
example, a noninverting gain of +2V/V configuration (R
F
= R ) using 1kΩ resistors, combined with 2pF of input
G
capacitance and 1pF of PC board capacitance, causes
a pole at 159MHz. Since this pole is within the amplifier
bandwidth, it jeopardizes stability. Reducing the 1kΩ
re s is tors to 100Ω e xte nd s the p ole fre q ue nc y to
1.59GHz, but could limit output swing by adding 200Ω in
parallel with the amplifier’s load resistor.
0–MAX4315
Table 1 shows suggested R and R values for the
F
G
__________Ap p lic a t io n s In fo rm a t io n
MAX4310/MAX4311/MAX4312 when operating in the
noninverting configuration (shown in Figure 1). These
values provide optimal AC response using surface-
mount resistors and good layout techniques, as dis-
cussed in the Layout and Power-Supply Bypassing
section.
Ra il-t o -Ra il Ou t p u t s , Gro u n d -S e n s in g In p u t
The input common-mode range extends from the nega-
tive supply rail to V
- 2.7V with excellent common-
CC
mod e re je c tion. Be yond this ra ng e , multip le xe r
switching times may increase and the amplifier output
is a nonlinear function of the input, but does not under-
go phase reversal or latchup.
Stray capacitance at the FB pin causes feedback resis-
tor decoupling and produces peaking in the frequency-
response curve. Keep the capacitance at FB as low as
p os s ib le b y us ing s urfa c e -mount re s is tors a nd b y
avoiding the use of a ground plane beneath or beside
these resistors and the FB pin. Some capacitance is
unavoidable; if necessary, its effects can be neutralized
The output swings to within 250mV of V and 40mV of
CC
V
EE
with a 10kΩ load. With a 150Ω load to ground, the
by adjusting R . Use 1% resistors to maintain consis-
tency over a wide range of production lots.
F
75Ω CABLE
R
75Ω
T
4
5
75Ω CABLE
IN0
OUT 8
FB 7
R
75Ω
T
Table 1. Bandwidth and Gain with
Suggested Gain-Setting Resistors
(MAX4310/MAX4311/MAX4312)
R
F
R
T
75Ω CABLE
75Ω
IN1
A0
R
75Ω
T
GAIN
(V/V)
GAIN
(dB)
R
(Ω)
R
(Ω)
-3dB BW
(MHz)
0.1dB BW
(MHz)
F
G
R
G
MAX4310
∞
500
120
56
1
2
0
6
0
280
80
60
30
4
1
500
500
500
5
14
20
20
Figure 1. MAX4310 Noninverting Gain Configuration
10
10
2
12 ______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
