Datasheet

17
LT1251/LT1256
TYPICAL APPLICATIONS
U
Logarithmic Gain Control (Noninverting)
Logarithmic Gain Control (Inverting)
1k
200Ω
200Ω
100pF
100pF
50Ω
1251/56 TA11
2
8
7
5, 4, 6
5V
10µF
2.5VDC
INPUT
V
OUT
14
13
121053
1
V
C
R
C
R
FS
V
FS
LT1251/LT1256
–
+
–
+
2
1
1k
10k
1k
1
2
3
1.6k
1.6k
–
+
LT1116
+
1.5k
1251/56 TA12
2
8
V
IN
V
OUT
C
C
THE TIME CONSTANT IS INVERSELY PROPORTIONAL TO V
C
.
R
DC
IS REQUIRED TO DEFINE THE DC OUTPUT WHEN
THE CONTROL IS AT ZERO.
14
13
121053
1
V
C
V
C
R
C
R
FS
V
FS
V
FS
LT1256
–
+
–
+
2
1
1.5k
R
R
R
DC
≅ 10k
T(s) =
–1
(s)(R)(C)
V
FS

V
C
()
1MHz Wien Bridge Oscillator Basic Variable Integrator
600Ω
200Ω
2k
6k
1.5k
V
IN
1251/56 TA07a
2
8
14
13
121053
1
V
OUT
2.5VDC
INPUT
V
C
CONTROL
VOLTAGE
R
C
R
FS
V
FS
9
7
V
+
V
–
LT1251/LT1256
–
+
–
+
2
1
6k
6k
1.5k
1.5k
V
IN
1251/56 TA08a
2
8
9
14
13
7
121053
1
V
OUT
2.5VDC
INPUT
V
C
CONTROL
VOLTAGE
R
C
R
FS
V
FS
V
+
V
–
LT1251/LT1256
–
+
–
+
2
1
CONTROL VOLTAGE (V)
0
GAIN (dB)
15
0
–15
1251/56 TA07b
1.25
2.5
V
FS
= 2.5V
A
V
= 24dB – 0.5
()
V
C

V
FS
<1dB ERROR
CONTROL VOLTAGE (V)
0
GAIN (dB)
15
0
–15
1251/56 TA08b
1.25
2.5
V
FS
= 2.5V
A
V
= 24dB – 0.5
()
V
C

V
FS
<1dB ERROR