Driving AD8302 using OP-amp
Hi
i am using AD8302 for gain and phase detection of two signals.
if i make use of only evaluation board supplying input signals from AFG3102C signal generator then i am getting perfect results in terms of Vmag. But
1. In case of Vphs it is changing with change in input signal amplitude. why it's happening?
2. when i give AD8302 INPB input directly from signal generator of 100mv(p-p),1Mhz and another input (INPA) is given using an op-amp (output of op-amp is the input of INPA) at same output level (100mv,1Mhz), Vmag and vphs gets changed.
its a very serious problem i think. please guide me to overcome this problem asap.
i appreciate your suggestions in advance.
Thanks
Harman baweja
Vector Power Measurement
RF Power Detectors
ad8302
To answer your questions:
1. In case of Vphs it is changing with change in input signal amplitude. why it's happening?
Answer: This is inherent in the design. It is most accurate when the signals are -30 dBm, or 20mVpp.
2. when i give AD8302 INPB input directly from signal generator of 100mv(p-p),1Mhz and another input (INPA) is given using an op-amp (output of op-amp is the input of INPA) at same output level (100mv,1Mhz), Vmag and vphs gets changed.
Answer: Have you probed INPA and INPB with an oscilloscope to confirm 100Vpp is being applied to both inputs? Your signal generator has a 50 Ohm output, while your op-amp should have a low output impedance. Your signal generator's signal level (Vpp) will change depending on what load impedance it sees.
Is the VPHS changing with time or is it fixed in time? When you probe the inputs I would note what the phase is doing. The VPHS could just be reporting what is going on on the inputs.
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Thank you,
EZ Admin
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