J2
THS3491RGT
+/-15V Split Bench
Power Supply
+15V
GND
-15V
THS3491RGT EVM
Signal Generator
Oscilloscope
(VS+)
(VS-)
-
+
287
Q
J3
50
Q
124
Q
0
Q
50
Q
J1
240
Q
240
Q
287
Q
54.9
Q
50
Q
Term
50
Q
Source
OUT
IN-
IN+
Voltage Gain = +5 V/V or 14 dB
Voltage Gain = 0.0436 V/V or -27.2 dB
FB
499
Q
EVM Default Configuration
3
SLOU483 – August 2017
Copyright © 2017, Texas Instruments Incorporated
THS3491RGT Evaluation Module
2
EVM Default Configuration
As delivered, the EVM has a fully functional example circuit; just provide power supplies, a signal source,
and a measuring instrument as shown in
. Some components, such as supply bypass capacitors
and test points, are omitted on the application schematics of
for clarity.
See
for the default schematic diagram of the THS3491RGT EVM.
Figure 1. THS3491RGT EVM Default Configuration Setup Block Diagram
2.1
Standard Non-Inverting Gain Configuration
The THS3491RGT EVM default configuration is a single-ended input, single-ended output non-inverting
gain of 5 from SMA input (J2) to the THS3491 device output pins as shown in
. The default
configuration for non-inverting gain of 5 is determined by R3, and R4 in
. This gain is calculated
according to
that is given below for non-inverting op-amp.
where
•
RF = 499
Ω
•
RG = 124
Ω
(1)
2.2
Output Voltage Loss Calculation to the Measuring Instrument
The THS3491RGT device output is driving an equivalent R
LOAD
= 100
Ω
determined by the output series
and parallel matching resistor network as shown in
. The output resistor network affects the
voltage that is measured at the SMA connector (J3). The designer should take into account the voltage
division from the device output to the SMA connector (J3) which is approximately 0.0436 or -27.2 dB given
by
. As a result, an overall voltage gain of –13.2 dB is achieved from SMA connector J2 to J3
for single-ended 50-
Ω
input and output.
