Datasheet

Using with Different Sources or Loads

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Figure 3. Input Schematic

The board was designed to be very flexible for many different configurations. Zoomed in portions of the

input and output schematics are shown above in Figure 2 and Figure 3. The evaluation board, as shipped,

has been optimized for ease of use with single ended 50 Ohm test equipment. This configuration may not

emulate the most common application circuits. The signal path schematic is shown in Figure 8 and the full

schematic in . PDF format is available upon request.

3 Using with Different Sources or Loads

The LMH6517EVAL-R1 evaluation board supports differential operation on both inputs and outputs.

However they will require additional components and some board rework. For driving the evaluation board

from a differential source, symmetrical signal paths are provided. Both input and output paths support fully

differential test equipment.

To drive the LMH6517EVAL-R1 evaluation board from a differential source, the transformers T3 and T4

must be removed. The diagrams in Figure 6 and Figure 7 show the required connections for differential

inputs. DC coupled operation is possible using differential signals. For DC coupled operation, make sure

that the test equipment can provide the 2.5 V offset voltage required.

For differential output signals remove transformers T1 and T2. Wire jumpers or zero Ohm resistors must

be added to complete the signal path across the transformer pads similar to the changes required for

differential inputs.

4 Other Board Configurations

For other applications or experiments there are many options for changing the output circuit to simulate

different circuit conditions. One option is to use a 2:1 transformer to simulate high impedance loads. In this

case one would use 100 Ohm resistors for R42, R43, R44 and R45. This would present a load of 200

Ohms to the amplifier output. Many common filter circuits have 200 Ohm input impedance. Other

combinations can also be used to simulate different load conditions. With a high impedance load the

capacitors C14 and C15 should be decreased to 1pF to avoid losing bandwidth.

AN-2081 LMH6517EVAL-R1 Evaluation Board SNOA553B–October 2010–Revised May 2013

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