# A little help with AC Sweep

#### borkoborko39

Joined Apr 16, 2017
4
Hi i have this scheme and i set AC Sweep to start frequency 1Hz, End frequency to 1000MHz, logarithmic decade 101.
I need to do Medium frequency voltage gain, Voltage gain factor Ku in db, Current gain KI in db. How do i find them?

#### Bordodynov

Joined May 20, 2015
2,469
Hi. Value R3 is bad. The transistor does not amplify.
Look at your simulator's voltage on the gate and on the drain.
The gate-source transition is biased in the forward direction!

#### Bordodynov

Joined May 20, 2015
2,469
See

#### borkoborko39

Joined Apr 16, 2017
4
Yes R3 should be 1.4Meg i mistyped it.

#### Jony130

Joined Feb 17, 2009
5,127
You need to set AC value to 1 and next you need to run ACsweep analysis then probe the voltage across R6. And the voltage gain is simply the voltage you read across R6. For example if the simulation will show you 10V the gain is 10[V/V]. And to plot the current gain use I(R6)/ I(V2).

Also can you tell my where I can buy 1.06μF and 6.83μF capacitors ?? The resistor values are also not standard ones .

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#### borkoborko39

Joined Apr 16, 2017
4
Okay i think i figured it out. Is this how the result is supposed to be?
Sheme

Medium Voltage Gain

Voltage Ku in Db

Voltage Ki in db

How do i find Kp in db? Db(W(R6)/W(V2))?

#### shteii01

Joined Feb 19, 2010
4,647
Do you need power in dB or dBm?
If I recall correctly, power is usually in dBm, but since I don't know your course... I am not sure which one of the two you need.

#### borkoborko39

Joined Apr 16, 2017
4
Do you need power in dB or dBm?
If I recall correctly, power is usually in dBm, but since I don't know your course... I am not sure which one of the two you need.
I need it dB. Is the other stuff right?

#### shteii01

Joined Feb 19, 2010
4,647
I don't think any of them are correct.

Your input signal is V2. Your output signal is voltage across R6. That is not what your graphs show.

The C1 and C3 capacitors are the DC Blocking Capacitors, they allow AC signals through, but block DC.