Datasheet
R
I
R
F
G=1
PGA112
PGA113
V
REF
V /2
S
V
IN0
V
IN1
V
OUT
CH0
CH1
MUX
+
-
V
OUT0
=G V AV /2 (G 1)´ - ´ -
IN0 DD
(2)
InputVoltage(V)
InputOffsetV
oltage( V)m
50
40
30
20
10
0
10
20
30
-
-
-
10 62 3 4 5
AV =5V
DD
OP AMP: GENERAL GAIN EQUATIONS
V =G (V +AV /2) /2 (G 1)
V =G V + /2,where: /2<G V <+ /2
´ -
OUT1 IN1 DD
- ´
´ - ´
AV
AV AV AV
DD
OUT1 IN1 DD DD IN1 DD
R
I
R
F
G=1
V
REF
V
IN
V
OUT
CH1
V =G V´
OUT IN
(1)
PGA112 , , PGA113
PGA116 , PGA117
SBOS424B – MARCH 2008 – REVISED SEPTEMBER 2008 ............................................................................................................................................
www.ti.com
Figure 72. PGA112/PGA113 Configuration for
Positive and Negative Excursions Around
Midsupply Virtual Ground
When: G = 1
Figure 70. V
OS
versus Input Voltage — Case 2
Then: V
OUT0
= G × V
IN0
Figure 71 shows the basic configuration for using the
PGA as a gain block. V
OUT
/V
IN
is the selected
(3)
noninverting gain, depending on the model selected,
Where:
for either binary or scope gains.
G = 1, 2, 4, 8, 16, 32, 64, and 128 (binary gains)
G = 1, 2, 5, 10, 20, 50, 100, and 200 (scope
gains)
Table 7 details the internal typical values for the op
amp internal feedback resistor (R
F
) and op amp
internal input resistor (R
I
) for both binary and scope
gains.
Table 7. Typical R
F
and R
I
versus Gain
Binary Scope
Gain Gain
Figure 71. PGA Used as a Gain Block
(V/V) R
F
( Ω ) R
I
( Ω ) (V/V) R
F
( Ω ) R
I
( Ω )
1 0 3.25k 1 0 3.25k
2 3.25k 3.25k 2 3.25k 3.25k
Where:
4 9.75k 3.25k 5 13k 3.25k
G = 1, 2, 4, 8, 16, 32, 64, and 128 (binary gains)
8 22.75k 3.25k 10 29.25k 3.25k
G = 1, 2, 5, 10, 20, 50, 100, and 200 (scope
16 48.75k 3.25k 20 61.75k 3.25k
gains)
32 100.75k 3.25k 50 159.25k 3.25k
Figure 72 shows the PGA configuration and gain
64 204.75k 3.25k 100 321.75k 3.25k
equations for V
REF
= AV
DD
/2. V
OUT0
is V
OUT
when
128 412.75k 3.25k 200 646.75k 3.25k
CH0 is selected and V
OUT1
is V
OUT
when CH1 is
selected. Notice the V
REF
pin has no effect for G = 1
because the internal feedback resistor, R
F
, is shorted
out. This configuration allows for positive and
negative voltage excursions around a midsupply
virtual ground.
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Product Folder Link(s): PGA112 PGA113 PGA116 PGA117