Texas Instruments THS4012 - Manual (Page 15)

Using the THS4012 EVM In The Inverting Mode
1-9 General
1.6 Using the THS4012 EVM In The Inverting Mode
The THS4012 EVM operates from power-supply voltages ranging from
±
5 V
to
±
15 V. As shipped, the EVM is configured for inverting operation. Move the
resistors as detailed above to configure the EVM for noninverting operation,
which sets the gain to –3. Signal inputs on the module are terminated for 50-
Ω
nominal source impedance. An oscilloscope is typically used to view and
analyze the EVM output signal.
1) Ensure that all power supplies are set to OFF before making power supply
connections to the THS4012 EVM.
2) Connect the power supply ground to the module terminal block (J2)
location marked GND.
3) Select the operating voltage for the EVM and connect appropriate split
power supplies to the module terminal block (J2) locations marked –VCC
and +VCC.
4) Connect an oscilloscope to the module SMA output connector (J3/J5)
through a 50-
Ω
nominal impedance cable (an oscilloscope having a 50-
Ω
input termination is preferred for examining very high frequency signals).
5) Set the power supply to ON.
6) Connect the signal input to the module SMA input connector (J1/J2).
Each EVM input connector is terminated with an equivalent 50-
Ω
impedance
to ground. With a 50-
Ω
source impedance, the voltage seen by the THS4012
amplifier IC on the module will be ½ the source signal voltage applied to the
EVM. This is due to the voltage division between the source impedance and
the EVM input terminating resistors (R1 || R4 and R9 || R12).
7) Verify the output signal on the oscilloscope.
The signal shown on an oscilloscope with a 50-
Ω
input impedance will be
½
the actual THS4012 amplifier IC output voltage. This is due to the voltage
division between the output resistor (R7, R15) and the oscilloscope input
impedance.