Datasheet

Noninverting Stage (Channel 2) Operation
3-4
3.2 Noninverting Stage (Channel 2) Operation
Noninverting stage operation was shown in Chapter 2 of this manual. The
defaultconfiguration isa 50-W terminated input(R8), a50-W matchingresistor
output(R11B),anda100-W load(R12B).Theterminatingandmatchingvalues
can be changed if the user requires different termination and matching—for
example, 75-W video applications. The load resistor, however, should not be
changedbecausemanyopampspecificationsaremeasuredatthisload.Gain
of the stage can be modified by changing the values of R9 and R10.
Figure 3--2.Noninverting Gain Stage
J9
OUT2
R12B
100
W
J7
+IN2
R8
49.9
W
R10
909
W
R9
909
W
R7
0
R11B
49.9
W
--
+
U1B
THS31x5PWP
12
11
13
Thegain ofthe circuitas populatedis 2with ahighimpedance load,and1 with
a 50-W load. This circuit does not exhibit the reduction in input voltage level
described for the inverting stage—as the input is connected directly to a high
impedance input of the op amp.
ThecircuitofFigure 3--2can beutilizedasavideodriverifthe 49.9-W resistors
are removed and 75-W resistors are substituted.
3.3 Shut Down Operation (Channels 1 and 2)
The output of channels 1 and 2 can both be shut down simultaneously when
a voltage above 2 VDC is applied to the shut down input (TP2 on the EVM).
In shut down mode, the output goes to ground. Normal operation is restored
for voltages below 0.8 V on the shut down input.