Datasheet

Evaluation Schematic
1-2
When used as an inverting amplifier in the default configuration connected to
a 50-Ω input measurement instrument, R7 causes a slight gain error. The total
voltage gain is the negative ratio of the feedback resistor R5 and the gain
resistor R3, times the voltage divider created by R6-R7, and the measurement
device input termination resistance. This gain follows the equation:
V
O
V
I
+ –
R5
R3
ǒ
R7 ø 50 W
R7 ø 50 W ) R6
Ǔ
+ –0.475
(1)
When using the default configuration, the noninverting gain of the amplifier is
affected by the same slight gain error, plus the gain error imposed by the invert-
ing input termination resistor R2. The following equation shows the gain for this
situation.
V
O
V
I
+
ǒ
1 )
R5
R3 ) R2
Ǔ
ǒ
R7 ø 50 W
R7 ø 50 W ) R6
Ǔ
+ 0.908
(2)
Some components such as C1, C2, C3, C4, C5, C6, TP1, J5, J6, and J7 are
omitted on the application schematics of Chapter 3 for clarity.
Figure 1-1. Schematic of the Populated Circuit on the EVM (Default Configuration)
TP1
*
Device not installed
J1
Vin
-
J4
Vout
R4
R2
J2
Vin+
-
+
U1
THS3061
2
3
6
7
4
R5
R6
R7
R3
J7J5
+
C2
-VS
+VS(IN)
FB2
+
C1
-
VS(IN)
FB1
+VS
U1A
C4
100 pF
C3
+VS
C5
-
VS
C6
J6
562 W
0.1 mF
562 W
54.9 W
49.9 W
953 W
0.1 mF
100 pF
49.9 W
22 mF