# Problem about Summing Amplifier on LTSPICE

#### cikalekli

Joined Dec 10, 2020
103
Hi,
I'm studying about summing amplifiers and try to make a proper circuit via on ltspice

You can find my .asc file and the screenshot of my graph.

My problem is I'm having trouble with trying getting a proper sin wave from Vout... I'm getting proper sin waves for inputs of V1 and V2 but Vout is just a mess ( I mean it has improper shape...)

Here is the Vout graph:

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#### Jony130

Joined Feb 17, 2009
5,230
So what? The author of a video is simply using a two voltage source (V1 and V2) with different amplitudes (1V and 2V ). But both of this voltage source has the same frequency (60Hz).

And in your simulation, we can see that you have set V1 = 1V and 5Hz and the second one 2V and 6Hz (different in frequqncy).

#### cikalekli

Joined Dec 10, 2020
103
So what? The author of a video is simply using a two voltage source (V1 and V2) with different amplitudes (1V and 2V ). But both of this voltage source has the same frequency (60Hz).

And in your simulation, we can see that you have set V1 = 1V and 5Hz and the second one 2V and 6Hz (different in frequqncy).
Yeah sorry about that. I just thought that whatever I use the hearts value then I'm gonna take the same shape of a sin wave as the author has shown in his video...

So I got it, thanks a lot, and let me ask one more question please:

Okay, so I have done this the simulation with ltspice but can you tell me that as an engineer, where do they use it and I have read about "gain" of it. So, how many gains did I observed, still I could not understand my simulation. Im just playing around on it to understand it but no... Still, this is my question and my main problem... Can you tell me about it or suggest to me a good source for investigating how many gains I did observe, please?

#### Alec_t

Joined Sep 17, 2013
12,065
The gain is the output amplitude divided by the input amplitude.

#### cikalekli

Joined Dec 10, 2020
103
The gain is the output amplitude divided by the input amplitude.
Oh, I got it, is there any good source to read more details of it please from basic level to the hard level?
Also happy new years...

#### DickCappels

Joined Aug 21, 2008
7,426
You can see how the circuit works very simply. Try this: Leave one voltage source as a sine wave source and the other source as a 1V DC source. What happened to your sine wave, and why?

#### ericgibbs

Joined Jan 29, 2010
12,901
hi c,
Check this out.
E

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#### Jony130

Joined Feb 17, 2009
5,230
Do you know the superposition principle?
For the V1 source we have an inverting amplifier with a voltage gain set by the ratio of A_V1 = - R1/R3 = 10K/10k = -1 V/V
And for the V2 we have a similar situation but this time the voltage gain is set by the ratio of A_V2 = - R1/R2 = -1V/V
And the voltage at the output will be the sum of the two voltages. V_out = V1 * A_V1 + V2 * A_V2

https://electronics.stackexchange.c...ound-principle-and-other-doubts/441207#441207