LM2902
DC SUMMING AMPLIFIER
e
1
100kΩ
ACTIVER BADPASS FILTER
R1
100k
Ω
C1
330pF
100kΩ
e
2
e
3
100kΩ
1/4
LM2902
e
O
e
1
1/4
LM2902
R4
10MΩ
C2
330pF
R5
470kΩ
1/4
LM2902
100kΩ
100kΩ
R3
10k
Ω
1/4
LM2902
R6
470kΩ
e
O
R7
100kΩ
V
CC
R8
100kΩ
C3
10
µ
F
e
4
100kΩ
eo = e1 + e2 - e3 - e4
where (e1 + e2)
≥
(e3 + e4)
to keep eo
≥
0V
Fo = 1kHz
Q = 50
Av = 100 (40dB)
HIGH INPUT Z ADJUSTABLE GAIN DC
INSTRUMENTATION AMPLIFIER
HIGH INPUT Z, DC DIFFERENTIAL AMPLIFIER
R1
100k
Ω
R2
100kΩ
R1
100kΩ
R3
100kΩ
1/4
LM2902
e
1
1/4
LM2902
R3
100k
Ω
R4
100k
Ω
R4
100kΩ
R2
2k
Ω
Gain adjust
1/4
LM2902
e
O
+V1
+V2
eo = [ 1 +
1/4
LM2902
V
o
R5
100k
Ω
R4 ] (e2 - e1)
R3
As shown eo = (e2 - e1)
1/4
LM2902
e
2
If R1 = R5 and R3 = R4 = R6 = R7
eo = [ 1 + 2R1 ] (e2 - e1)
R2
As shown eo = 101 (e2 - e1)
R6
100k
Ω
R7
100k
Ω
LOW DRIFT PEAK DETECTOR
USING SYMMETRICAL AMPLIFIERS TO
REDUCE INPUT CURRENT (GENERAL
CONCEPT)
I
B
1/4
I
B
LM2902
1/4
I
e
o
Z
o
I
I
B
LM2902
2N 929
µ
0.001 F
e
o
e
I
1/4
LM2902
I
B
e
I
Z
I
1
µ
F
C
*
2I
B
2N 929
2I
B
R
1MΩ
0.001
µ
F
I
B
3R
3MΩ
I
B
1/4
LM2902
I
B
I
B
3MΩ
I
B
1/4
LM2902
Input current
compensation
Aux. amplifier for input
current compensation
* Polycarbonate or polyethylene
1.5MΩ
7/11
STMICROELECTRONICS [ STMICROELECTRONICS ]
