LT6600IS8-20#PBF Linear Technology, LT6600IS8-20#PBF Datasheet - Page 9

• Manufacturer Part Number: LT6600IS8-20#PBF
• Description: IC AMP DIFF LP FLTR 20MHZ 8-SOIC
• Manufacturer: Linear Technology

Specifications of LT6600IS8-20#PBF

• Amplifier Type: Differential
• Number Of Circuits: 1
• Output Type: Differential
• Current - Input Bias: 50µA
• Voltage - Input Offset: 10000µV
• Current - Supply: 46mA
• Voltage - Supply, Single/dual (±): 3 V ~ 11 V, ±1.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• No. Of Amplifiers: 1
• Input Offset Voltage: 35mV
• Gain Db Max: 12.6dB
• Bandwidth: 20MHz
• Supply Voltage Range: 3V To 11V
• Supply Current: 42mA
• Amplifier Case Style: SOIC
• No. Of Pins: 8
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output / Channel: -
• -3db Bandwidth: -
• Slew Rate: -
• Gain Bandwidth Product: -

APPLICATIONS INFORMATION
place well before the output stage of the fi lter reaches the
supply rails, the input/output behavior of the IC shown
in Figure 6 is relatively independent of the power supply
voltage.
The two amplifi ers inside the LT6600-20 have indepen-
dent control of their output common mode voltage (see
the Block Diagram section). The following guidelines will
optimize the performance of the fi lter.
Pin 7 must be bypassed to an AC ground with a 0.01μF or
larger capacitor. Pin 7 can be driven from a low impedance
source, provided it remains at least 1.5V above V
least 1.5V below V
voltage of Pin 7. While the internal 11k resistors are well
matched, their absolute value can vary by ±20%. This
should be taken into consideration when connecting an
external resistor network to alter the voltage of Pin 7.
Pin 2 can be shorted to Pin 7 for simplicity. If a different
common mode output voltage is required, connect Pin 2
to a voltage source or resistor network. For 3V and 3.3V
supplies the voltage at Pin 2 must be less than or equal to
the mid supply level. For example, voltage (Pin 2)≤1.65V
on a single 3.3V supply. For power supply voltages higher
than 3.3V the voltage at Pin 2 should be within the voltage
of Pin 7 – 1V to the voltage of Pin 7 + 2V. Pin 2 is a high
impedance input.
–100
–120
–20
–40
–60
–80
20
Figure 6. Output Level vs Input Level,
Differential 1MHz Input, Gain = 1
0
0
COMPRESSION POINTS
3RD HARMONIC
1dB PASSBAND GAIN
1
3RD HARMONIC
+
. An internal resistor divider sets the
1MHz INPUT LEVEL (V
2
25°C
85°C
3
4
2ND HARMONIC
85°C
1MHz 85°C
2ND HARMONIC
25°C
5
P-P
1MHz 25°C
)
6
66002 F06
7
–
and at
The LT6600-20 was designed to process a variety of input
signals including signals centered around the mid-sup-
ply voltage and signals that swing between ground and
a positive voltage in a single supply system (Figure 1).
The range of allowable input common mode voltage (the
average of V
the power supply level and gain setting (see Distortion
vs Input Common Mode Level in the Typical Performance
Characteristics section).
Common Mode DC Currents
In applications like Figure 1 and Figure 3 where the
LT6600-20 not only provides lowpass fi ltering but also level
shifts the common mode voltage of the input signal, DC
currents will be generated through the DC path between
input and output terminals. Minimize these currents to
decrease power dissipation and distortion.
Consider the application in Figure 3. Pin 7 sets the output
common mode voltage of the 1st differential amplifi er inside
the LT6600-20 (see the Block Diagram section) at 2.5V.
Since the input common mode voltage is near 0V, there
will be approximately a total of 2.5V drop across the series
combination of the internal 402Ω feedback resistor and the
external 100Ω input resistor. The resulting 5mA common
mode DC current in each input path, must be absorbed by
the sources V
output voltage of the 2nd differential amplifi er inside the
LT6600-20, and therefore sets the common mode output
voltage of the fi lter. Since, in the example of Figure 3, Pin 2
differs from Pin 7 by 0.5V, an additional 2.5mA (1.25mA
per side) of DC current will fl ow in the resistors coupling
the 1st differential amplifi er output stage to fi lter output.
Thus, a total of 12.5mA is used to translate the common
mode voltages.
A simple modifi cation to Figure 3 will reduce the DC com-
mon mode currents by 36%. If Pin 7 is shorted to Pin 2 the
common mode output voltage of both op amp stages will
be 2V and the resulting DC current will be 8mA. Of course,
by AC coupling the inputs of Figure 3, the common mode
DC current can be reduced to 2.5mA.
IN
IN
+
+
and V
and V
IN
IN
–
–
. Pin 2 sets the common mode
in Figure 1) is determined by
LT6600-20
66002fb
9