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LMH0001: Output impedance and why the 75-ohm resistors are required

Navneet Gandhi
Prodigy 60 points
Part Number: LMH0001

Hi,

I'm looking at the main application circuit in the datasheet

1. Can you help me understand what the output impedance is of LMH0001?

2. It appears that two of the 75-ohm are being used as series termination resistors, is that correct?

3. Why are there two more 75-ohm resistors tied to VCC? What do they achieve?

4. What do the two 5.6nH inductors do?


Thanks in advance!

  • +1
    TI__Guru* 92840 points

    Hi Navneet,

    1). LMH0001 impedance is set by 75-ohm to Vcc. So in the main application diagram on first page, output impedance is 75 ohm.

    2). 75-ohm in parallel with 5.6nH inductors are used for return loss network and this is correct.

    3). These two Resistors sets up the cable driver impedance. This matches the coax impedance being driven by LMH0001.

    4). 5.6nH in parallel with 75-ohm sets up the impedance across frequency and matches the coax or 75-ohm cable that is being driven.

    Regards, Nasser