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THS 4531 output voltage to small

Other Parts Discussed in Thread: THS4531, OPA820, LMH6559

I am using THS 4531 EVM. When i test it by giving a 1V sinusoid input, measure the output using a scope, the output is very small - about -38dB loss. Apparently, this is due to the fact that scope has a 50 Ohm termination?

How can we configure the EVM so that the output is the same as input - i.e. unity gain, as advertised in the data sheet? 

thanks

Gaurav

  • Hello Gaurav,

    The EVM is configured in such a way that the differential output of THS4531 is attenuated using resistors R20, R21 and R24 and converted to single ended using transformer T2. This is done for observing the differential output waveform when connected to 50 ohm oscilloscope while providing 2kohm differential load to amplifier. This is the reason for the attenuation.

    For measuring the output directly, populate R22 and R23 with 50 Ohms and connect J5 and J6 to  a two channel oscilloscope with 50 ohm termination and perform (CH1-CH2) operation if available. The differential load to the amplifier will now be 200 Ohms.

    Thanks and regards,

    Eldho

  • Hi Eldho,

    I would like to use the EVM as single ended input (SMA), single ended output and have it act like a unity gain buffer. This is how the product is advertised, this is what we have purchased. Please advise the configuration to do that. In its default mode, the product does not behave like that.

    thanks,

    Gaurav

  • Hello Gaurav,

    If you want a single ended input, single ended output buffer it may be better to purchase a standard op amp. 

    Would the OPA820 be suitable?

    Also the LMH6559 is also a single ended input/output buffer.

    Regards,

    Loren