LT1994 Linear Technology, LT1994 Datasheet - Page 17

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

TYPICAL APPLICATIO S
Differential 1st Order Lowpass Filter
Maximum –3dB frequency (f
Stopband attenuation: –6dB at 2 • f
Component Calculation:
1. Calculate an absolute value for C11 (C11
2. Select a standard 5% capacitor value nearest the absolute
3. Calculate R11 and R21 using the standard 5% C11
C
R11 = R12, R21 = R22
specifi ed –3dB frequency
value for C11
value, f
R11 and R21 equations (C11 in pF and f
R
R
f
11
3
21
11
dB
abs
=
=
≤
=
159 2 10
Gain
5
R
3dB
C
MHz and Gain
21
4 10
V
V
11
IN
IN
0.1µF
f
•
. •
3
–
+
and desired gain
dB
•
f
3
R11
R12
5
dB
(
6
C
11
1
2
8
abs
7
V
–
+
≤
+
LT1994
3
in pF and f
6
5
+
–
C11
R21
R22
C12
f
MHz
3
3dB
4
5
dB
0.1µF
) 5MHz
3dB
U
and 14dB at 5 • f
3
dB
V
V
1994 TA03
OUT
OUT
in kHz
3dB
+
–
abs
in kHz)
) using a
)
3dB
Example: The specifi ed –3dB frequency is 1MHz Gain = 4
1. Using f
2. Nearest standard 5% value to 400pF is 390pF and C11
3. Using f
Differential 2nd Order Butterworth Lowpass Filter
Maximum –3dB frequency (f
Stopband attenuation: –12dB at 2 • f
Component Calculation:
= C12 = 390pF
= R22 = 412Ω and R11 = R12 = 102Ω (nearest 1%
value)
R11 = R12, R21 = R22, R31 = R32, C21 = C22,
C11 = 10 • C21, R1 = R11, R2 = R21, R3 = R31,
C2 = C21 and C1 = C11
V
V
IN
IN
–
+
3dB
3dB
R11
R12
C11
= 1000kHz, C11 = 390pF and Gain = 4, R21
= 1000kHz, C11
0.1µF
R21
R31
R32
R22
3dB
1
2
8
abs
7
+
V
–
+
) 2.5MHz
3
LT1994
www.DataSheet4U.com
6
= 400pF
+
–
3dB
C21
C22
4
5
0.1µF
and –28dB at 5 • f
LT1994
V
V
1994 TA04
OUT
OUT
17
+
–
1994fa
3dB