RF chock DC block cancels my small signal totally in LTSPICE

Thread Starter

yef smith

Joined Aug 2, 2020
717
Hello, I am building a Common source amplifier as shown bellow.
As you can see bellow The Vsource signal is good sinus.
but after the capacitor the sinus is totally canceled and i got only the DC bias.
I am supposed to see the sinous with DC offset after the C2 capacitor.
Where did i go wrong?
Thanks.

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Bordodynov

Joined May 20, 2015
3,177
L1 is very small and it ruins the signal. Put an inductance value of 1 mH. In general you can use a resistor instead of inductance in that circuit. Use a 100 kOhm resistor. Also increase the capacitor value. Inductance and capacitance form a voltage divider. Calculate their inductance and capacitor values at 10000 Hz.
 

Thread Starter

yef smith

Joined Aug 2, 2020
717
Hello ,my formal work frequency is 100Mhz, so i want my AC signal to pass .
I will use C=1.59*10^-9 to get |Zc|=1ohm
For RF choke i put so RF will tacke high resistance and DC will tack no resistance. 1mH Z_L=2*100*10^6*1mH=6.28*10^5Ohm

What real world values do you recomment for RF CHOKE and DC BLOCK
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