LM2902
TYPICAL SINGLE - SUPPLY APPLICATIONS
ACTIVER BANDPASS FILTER
HIGH INPUT Z, DC DIFFERENTIAL AMPLIFIER
R1
100k
Ω
C1
330pF
R
1
R
4
=
R
2
R
3
(CMRR depends on this resistor ratio match)
For
1/4
LM2902
e
1
R4
10M
Ω
C2
330pF
R5
470k
Ω
1/4
LM2902
R2
100k
Ω
R1
100k
Ω
1/4
LM29 02
e
O
R4
100k
Ω
R3
100k
Ω
1/4
LM29 0 2
R3
10k
Ω
1/4
LM2902
R6
470k
Ω
R7
100k
Ω
V
CC
R8
100k
Ω
C3
10
µ
F
+V1
+V2
V
o
R
4
) (
e
2
−
e
1
)
R
3
As shown e
o
= (e
2
- e
1
)
e
o
(1+
F
O
= 1kHz
Q = 50
A
V
= 100 (40dB)
USING SYMMETRICAL AMPLIFIERS TO REDUCE INPUT CURRENT (GENERAL CONCEPT)
I
I
e
I
I
B
I
B
LM2902
1/4
e
o
2N 929
0.001
µ
F
I
B
I
B
3M
Ω
1/4
LM2902
1.5M
Ω
I
B
Aux. a mplifier for input
current compe ns a tion
9/14