Datasheet

Direct Feedback Amplifier
G +
R
3
2
) R
5
R
5
)
1
2 g
m
[ 1 )
R
3
2R
5
(5)
I
OUT
+
R
1
R
2
I
IN
I
OUT
I
IN
R
1
R
2
I
OUT
+
1
C R
ŕ
I
IN
dt
I
OUT
I
IN
C
R
I
OUT
+ *
ȍ
n
j+1
I
j
I
OUT
I
2
I
n
I
1
I
OUT
+ *
ȍ
n
j+1
I
j
R
j
R
I
OUT
I
1
R
R
1
I
n
R
R
n
OPA860
SBOS331C – JUNE 2005 – REVISED AUGUST 2008 ....................................................................................................................................................... www.ti.com
The gain for this topology is given by Equation 5 :
The direct feedback amplifier (shown in Figure 53 )
topology has been used to characterize the OPA860.
Extended characterization of this topology appears in
the Typical Characteristics section of this data sheet.
This topology is obtained by closing the loop between
the C-output and the E-input of the common-E
topology, and then buffered.
Table 1. Current-Mode Analog Computation Using the OTA Section
FUNCTIONAL ELEMENT TRANSFER FUNCTION IMPLEMENTATION WITH THE OTA SECTION
Current Amplifier
Current Integrator
Current Summer
Weighted Current Summer
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