Datasheet

C
1
C
2
V
IN
R
R
V
OUT
C C
1 2
+
Q =
C C
1 2
w
0
+
1
C
1
C
2
Ǹ
R
V
OUT
V
IN
1
1 + sR(C + C ) + s C C R
2 1 2
2 2
1
=
20
Ω
20
Ω
R
2
100k
Ω
V
IN
R
2
100
Ω
R
1
40.2
Ω
CCII
B
3
2E
C8
V
OUT
V
REF
C
1
100pF
D
1
D
2
OPA656
The OTA amplifier works as a current conveyor (CCII) in this circuit, with a current gain of 1.
R
1
and C
1
set the DC restoration time constant.
D
1
adds a propagation delay to the DC restoration.
R
2
and C
1
set the decay time constant.
D
1
, D
2
= 1N4148
R
Q
= 1k
Ω
JFET−Input, Wideband
V
OUT
5
BUF602
6
2
3
33
Ω
10pF
10
Ω
2
8
10
Ω
8
33
Ω
10pF
V
IN
180
Ω
6
V
REF
180
Ω
3
OPA861
www.ti.com SBOS338G –AUGUST 2005–REVISED MAY 2013
Figure 37. Control-Loop Amplifier Using Three OPA861s
Figure 38. DC Restorer Circuit
Negative Impedance Converter Filter: Low-Pass
The transfer function is shown in Equation 5:
Filter
The OPA861 can be used as a negative impedance
converter to realize the low-pass filer shown in
(5)
Figure 39.
with:
Figure 39. Low-Pass Negative Impedance
Converter Filter
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