R
3
R
1
J
2
-
In
R
7
49.9
W
J
4
+In
J
3
Out
J
6
Enable/
Disable
R
4
C
1
(Optional)
+VS
R
2
R
5
49.9
W
R
8
49.9
W
3
5
4
6
U1
2
1
C
2
2.2 F
m
+
C
3
0.1 F
m
-
VS
C
4
0.1 F
m
+
C
5
2.2 F
m
+VS
J
5
R
6
3
1
-VS
2
5
6
PD
OUT
V
S+
V
S
±
Circuit
2
SBOU232 – October 2019
Copyright © 2019, Texas Instruments Incorporated
DEM-OPA-SC-1A-EVM Evaluation Module
All high-frequency devices have a common sensitivity to component and layout parasitics that may alter
the AC performance. Therefore, slight adjustments of the feedback resistor, the gain resistor, or both
might be necessary to obtain the final desired frequency response. For current feedback amplifiers,
increasing RF from its nominal value will reduce the achievable bandwidth, while decreasing RF will cause
the frequency response to peak more. However, at higher gains, it might be advantageous to decrease RF
to optimize for bandwidth.
For voltage feedback amplifiers, changing the impedance level (increasing or decreasing RF and RG) can
also control the amount of peaking.
Figure 1. SC70 (DCK) Package Pinout, Top View
2
Circuit
The circuit schematic in
shows the connections for all possible components. Each configuration
uses only some of the components. The power-supply bypassing capacitors are crucial components for
high-frequency amplifiers and should not be omitted during evaluation. Typically, each supply should be
bypassed by a parallel combination of a ceramic 0.1-
μ
F capacitor and a tantalum 2.2-
μ
F capacitor. Those
bypass capacitors are located on the board such that the return path to the power connector is very short.
Any larger transient currents will have a short loop, and will not reflect to the input and cause an increase
in distortion.
Figure 2. DEM-OPA-SC-1A Schematic