TS615IPWT View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
TS615IPWT Datasheet PDF : 27 Pages
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TS615
CHOICE OF THE FEEDBACK CIRCUIT
Table 71 : Closed-Loop Gain - Feedback Compo-
nents
VCC (V)
±6
±2.5
Gain
+1
+2
+4
+8
-1
-2
-4
-8
+1
+2
+4
+8
-1
-2
-4
-8
Rfb (Ω)
750
680
620
510
680
680
620
510
1.1k
1k
910
680
1k
1k
910
680
INVERTING AMPLIFIER BIASING
In this case a resistance is necessary to achieve a
good input biasing, as R on (fig.30).
This resistance is calculated by assuming the neg-
ative and positive input bias current. The aim is to
make the compensation of the offset bias current
which could affect the input offset voltage and the
output DC component. Assuming Ib-, Ib+, Rin, Rfb
and a zero volt output, the resistance R comes: R
= Rin // Rfb .
Figure 72 : Compensation of the Input Bias
Current
Rfb
Ib-
Rin
_
Vcc+
TS615
+
Ib+
Vcc-
R
Output
Load
ACTIVE FILTERING
Figure 73 : Low-Pass Active Filtering. Sallen-Key
R1
IN
C1
R2
+
C2
TS615
_
OUT
25Ω
Rfb
RG
910Ω
The resistors Rfb and RG give directly the gain of
the filter as a classical non-inverting amplification
configuration :
AV = g = 1 + R--R---f-g-b--
Assuming the following expression as the re-
sponse of the system:
Tjω = -V--V--o--i--un---j-t-ωj--ω--- = 1-----+-----2----ζ----ω-j----ω--g--c-----+------(---ω--j----ω---c-----)--2---2----
the cutoff frequency is not gain dependent and it
comes:
ωc
=
------------------1-------------------
R1R2C1C2
the damping factor comes:
ζ = 12-- ωc(C1R1 + C1R2 + C2R1 – C1R1g)
The higher the gain the more sensitive the damp-
ing factor is. When the gain is higher than 1 it is
preferable to use some very stable resistors and
capacitors values.
24/27
In the case of R1=R2:
ζ = 2----C-----2-----–----C-----1----R---R------f--g--b----
2 C1C2
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