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LMH2110TMEVAL: Output Signal Not Adequate as Input for LM311

Gustavo Chacon
Prodigy 30 points
Part Number: LMH2110TMEVAL
Other Parts Discussed in Thread: LM311, LMH2110, TLV3601, TLV3201, TLV3501

Hi - I am using LMH2110TMEVAL board to measure the power from a received wireless signal. The voltage measure is about 0.6V which is expected.

The output is then the inverting input for LM311 to be compare to the noninverting input of LM311 which is 0.4V. The output of the LM311 (collector to 5V and emitter to a resistor and then to ground). LM311 is not comparing properly: output from emitter pin not as expected.

Then, replaced the LMH2110TMEVAL signal for the inverting input with a voltage signal from a power supply with 0.6V and very low current, and the output of the described circuit is as expected.

What am I missing? Why isn't LMH2110TMETAL performing as expected? Checked the datasheet of LMH2110 and does not seem that I am missing something. Tried added a opamp based buffer between LMH2110TMEVAL and the LM311 but didn't work.

Thanks in advance for any help you could provide,

Gus  

  • 0
    TI__Guru 55596 points

    Hello Gustavo,

    Please provide an exact schematic of your circuit, including expected signal levels, pulse widths and supply voltages.

    The LM311 has a limited input range that does NOT include ground. The input is limited to about 0.5V above Vcc- and 1.2V below Vcc+ (this was designed as a 30V device, and performance is worse at low supply voltages). There are much better alternatives these days...

  • 0 in reply to Paul Grohe
    Prodigy 30 points

    Hi Paul - Thanks for your reply, the schematic is as follows:

    What alternative would you recommend instead of LM311?

    Thanks again!

  • 0 in reply to Gustavo Chacon
    TI__Guru 55596 points

    Hello Gustavo,

    Sorry for the delay.

    We have many new high speed options. What is the minimum pulse width of your signal?

    We have options with speeds from 40ns to 2.5ns, with conventional or LVDS outputs.

    See the TLV3201, TLV3501 and TLV3601 families.

  • 0 in reply to Paul Grohe
    Prodigy 30 points

    Hi Paul - sorry for my late response. Do you have another comparators with fast response but rated for 10V or higher?