LT1994 Linear Technology, LT1994 Datasheet - Page 18

• Manufacturer Part Number: LT1994
• Description: Low Noise - Low Distortion Fully Differential Input/Output Amplifier/Driver
• Manufacturer: Linear Technology

LT1994
TYPICAL APPLICATIO S
1. Calculate an absolute value for C2 (C2
2. Select a standard 5% capacitor value nearest the absolute
3. Calculate R3, R2 and R1 using the standard 5% C2
18
specifi ed –3dB frequency
value for C2 (C1 = 10 • C2)
value, the specifi ed f
gain (Gn)
R1, R2 and R3 equations (C2 in pF and f
C
R
R
R
f
3
2
3
2
1
dB
abs
=
=
=
≤
R
Gn
(
R
1 121
=
2 5
2
1 266 10
3
.
.
.
4 10
•
MHz and Gain
C
f
•
3
2
A Single Ended to Differential Voltage Conversion with Source Impedance Matching and Level Shifting
dB
–
2
•
–1
5
1
0
•
(
f
(
(
Gn
3
V
C
1 131 0 127
15
dB
V
V
2
.
IN
IN
+
2
abs
3dB
1
)
R
in pF and f
– .
S
•
≤
= 50Ω
C
and the specifi ed passband
8 8
2
.
•
f
3
or Gain
U
d d B
50Ω
•
Gn
3
t
dB
0.1µF
)
54.9Ω
)
in kHz Note
•
374Ω
≤
10
402Ω
3dB
2 5
abs
.
8
f
3
) using a
) (
MHz
in kHz)
(
dB
Note
1
2
8
7
V
V
–
+
OCM
+
3
402Ω
+
–
6
402Ω
1
2 2 )
)
LT1994
4
5
0.1µF
Example: The specifi ed –3dB frequency is 1MHz Gain = 1
1. Using f
2. Nearest standard 5% value to 400pF is 390pF and C21
3. Using f
= C22 = 390pF and C11 = 3900pF
= 549Ω, R2 = 549Ω and R3 = 15.4Ω (nearest 1%
values). R11 = R21 = 549Ω, R21 = R22 = 549Ω and
R31 = R32 = 15.4Ω.
Note 1: The equations for R1, R2, R3 are ideal and do
not account for the fi nite gain bandwidth product (GBW)
of the LT1994 (70MHz). The maximum gain is set by
the C1/C2 ratio (which for convenience is set equal to
ten).
Note 2: The calculated value of a capacitor is chosen
to produce input resistors less than 600Ω. If a higher
value input resistance is required then multiply all resis-
tor values and divide all capacitor values by the same
number.
V
V
OUT
OUT
–
+
3dB
3dB
V
V
OCM
OCM
= 1000kHz, C2
= 1000kHz, C2 = 390pF and Gain = 1, R1
+ 0.25V
– 0.25V
V
OCM
0
V
abs
= 400pF
V
V
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OUT
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+
–
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