I have used Cblock, Cbypass of 10nF each, RFC 150uH, Rbias of 47ohm and Vd =9.4V. But I am not getting any positive gain. What could be the problem here? How can I start debugging the circuit?
Pay attention the input of this amplifier.If you apply a high RF power, the amplifier may be easily burned.( Emitter followers cannot resist to high input levels.)
Instead, increase the RF level incremently and observe the SA.
The simplest way to find if an MMIC is still alive, measure the DC voltage referenced to the ground on PIN 1, and the voltage should be somewhere between 1.5V and 2V.
Ok, I applied a 9.4V as Vd, and got 5.01V at Pin3. I tried to add another 50ohm parallel to reduce the drop across R, but still the Pin3 voltage could go upto 5.15V only. The device operating voltage is 5.4 to 6.2V, means the device is not having the right Vd. If I try to increase the Vd, the current drawn increases, but not the voltage at pin 3. What could be the problem?
I used the same value of resistor as given in the recommended ckt in datasheet and was able to get the amplifier working, but it is giving positive value of S11 at certain band, what could be the issue? Measurement was done on VNA after calibration.
um. I would rather expect 3 or 4 vias than just one. Ground inductance can definitely cause negative input impedance (S11 outside the unit circle in smith chart).
Thanks FvM! I have fabricated another board with 3 via holes and now S11 at the said frequency is -6.9dB. I was expecting a value lower than -10dB. Anyway, the new issue is that I am getting a S11 phase zero cross over every 100MHz, and the s2p on datasheet shows phase cross over only at 2GHz interval. Would it be the input and output transmission lines that I have added that generates those multiple zero phase cross overs? How can I fix this?
Get rid of the 100uH RFC . you're probably oscillating at 160MHz due to SRF and causing 360 deg cycles of phase shift of interference every 160MHz on the sweep. THis may allow pin 3 to rise
After changing the dc block capacitors at input and output to a lower value of 1pF, S11/S22 phase variation is settled, but S21 phase variation is still an issue. Any suggestions to fix the S21 phase?
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I checked the amp ckt to a spectrum analyser and couldn't find any oscillations.