As datasheet says HMC900LP5E has 2vppd output and LTC2387 has maximum 4.096V diff-input. i want to use the whole range of LTC2387. Is there any way i Can use this low pass filter in front of this ADC (ltc2387) through which the full scale range of LTC2387 can be used?
It sounds like you need at least a dual channel, differential 6 dB amp?
So before this low pass filter i have gain block. i can supply signal with full range of HMC900 (2Vppd). but then at its output i need 4Vp-p for ltc2387.
I can use max gain but still then i will not have 4vppd at the output right ?
HMC900 full-scale output is 2Vpp, whether the gain is set to 0 dB or 10 dB. Input full-scale changes accordingly with the gain, i.e. the output sets the full-scale.
So if you set the HMC900 to 0 dB gain, you could drive its input to 2Vpp, you'd have 2Vpp on its outputs, but would need a 6 dB amp to get to 4 Vpp.
If you set the HMC900 to 10 dB gain, you could only drive its input to 0.613 Vpp, you'd have 2Vpp on its outputs, and would still need a 6 dB amp to get your signal to 4 Vpp.
Keep in mind that these numbers assume a 400 Ohm load. If the load is reduced, the full-scale voltage would be reduced, as shown in the datasheet.
Thank you jdobler