Datasheet

LT1994
18
1994fb
3. Calculate R3, R2 and R1 using the standard 5% C2
value, the specifi ed f
3dB
and the specifi ed passband
gain (Gn)
f MHz and Gain or Gain
MHz
f
dB
dB
3
3
188
1
≤≤≤.
R1, R2 and R3 equations (C2 in pF and f
3dB
in kHz)
R
Gn
Gn C f
3
1 121 1 131 0 127 10
12
8
3
=
()
()
+
()
.– .–. • •
••
ddB
dB
Note
R
RC f
R
R
Gn
()
.•
••
1
2
1 266 10
32
1
2
15
2
3
2
=
=
Example: The specifi ed –3dB frequency is 1MHz Gain = 1
1. Using f
3dB
= 1000kHz, C2
abs
= 400pF
2. Nearest standard 5% value to 400pF is 390pF and C21
= C22 = 390pF and C11 = 3900pF
3. Using f
3dB
= 1000kHz, C2 = 390pF and Gain = 1, R1
= 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.
A Single-Ended to Differential Voltage Conversion with Source Impedance Matching and Level Shifting
1994 TA05
+
–
–
+
V
+
V
t
0.1µF
3
7
6
8
1
2
5
4
R
S
50
374
50
54.9
402
402
402
0.1µF
V
IN
V
IN
LT1994V
OCM
V
OUT
+
V
OUT
–
V
OCM
– 0.25V
V
OCM
+ 0.25V
V
OUT
–
V
OUT
+
V
OCM
0
1
–1
V
t
0
TYPICAL APPLICATIONS