OP177
PRECISION POSITIVE PEAK DETECTOR
In Figure 31, C
H
must be polystyrene, Teflon®, or polyethylene
to minimize dielectric absorption and leakage. The droop rate is
determined by the size of C
H
and the bias current of the AD820.
+15V
R
S
1kΩ
R
1
2kΩ
0.1µF
2
3
C
C
R
F
100kΩ
PRECISION THRESHOLD DETECTOR/AMPLIFIER
In Figure 32, when V
IN
< V
TH
, amplifier output swings negative,
reverse biasing diode D
1
.
V
OUT
= V
TH
if R
L
= ∞. When V
IN
≥
V
TH
, the loop closes.
V
TH
V
IN
–
+
7
6
D
1
1N4148
OP177
V
OUT
4 0.1µF
00289-032
⎛
R
⎞
V
OUT
=
V
TH
+
(
V
IN
−
V
TH
)
⎜
1
+
F
⎟
⎜
R
S
⎟
⎝
⎠
C
C
is selected to smooth the response of the loop.
–15V
Figure 32. Precision Threshold Detector/Amplifier
Rev. E | Page 12 of 16
AD [ ANALOG DEVICES ]
