What is the output voltage in this circuit?

dexterdev · Feb 13, 2012

View attachment 61072
I would like to know the output voltage in this circuit at label A. (I am a beginner , sorry for stupid questions if any? )

The circuit setup is a sine wave source (ideal) in parallel with DC source series with a resistor.

-Devanand T

canadaelk · Feb 13, 2012

Provided that the sinewave source is DC blocking and of low output impedance, you have the 1VAC (centered) riding on 1VDC.
Why not simulate it in the free LTSpice? E
PS: there is never (correction: seldom) such a thing as a stupid question

dexterdev · Feb 13, 2012

canadaelk said:
Provided that the sinewave source is DC blocking

what does that mean?

Why not simulate it in the free LTSpice?

I would like to know the reasons. Simulation will give result only.

Ratchit · Feb 13, 2012

dexterdev,

I would like to know the output voltage in this circuit at label A.

Point A is the measurement across the AC voltage, so the AC source will determine what the voltage will be. The DC source only determines the amount, direction, and type of current existing in the circuit.

Ratch

WTP Pepper · Feb 13, 2012

Assume your AC signal is goes from -1V to +1V (i.e.it has no DC component itself - DC blocking) then when the sine wave is at -1V, it is added to the +1V of the DC source which gives you 0V. When the sine wave is at +1V and added to the 1V DC source, the output is 2V, so as canadaelk has aleady pointed out, it'a a 1V sinewave sat on a 1V DC level. What used to vary from -1V to +1V now varies from 0C to +2V.

dexterdev · Feb 13, 2012

thakyou for the reply sir, but I have still doubts (no one else for help)

Ratchit said:
Point A is the measurement across the AC voltage,
Ratch

but point A is also across DC source in series to resistor.

so the AC source will determine what the voltage will be. The DC source only determines the amount, direction, and type of current existing in the circuit.

why AC source determines the output voltage

audioguru · Feb 13, 2012

WTP Pepper said:
Assume your AC signal is goes from -1V to +1V (i.e.it has no DC component itself - DC blocking) then when the sine wave is at -1V, it is added to the +1V of the DC source which gives you 0V. When the sine wave is at +1V and added to the 1V DC source, the output is 2V, so as canadaelk has aleady pointed out, it'a a 1V sinewave sat on a 1V DC level. What used to vary from -1V to +1V now varies from 0C to +2V.

We don't know enough about the signal source to determine the output voltage of this circuit.
Is it a signal generator with an average DC output of 0V but an output impedance of 50 ohms?
Is the signal from an amplifier that has an extremely low output impedance and an average output of 0V?
Or does the signal generator have an output coupling capacitor?
Does the signal generator have a high output impedance so that the 50 ohms load here shorts its signal?

dexterdev · Feb 13, 2012

Can you please explain for each case? ie
if signal generator has average DC output of 0V but an output impedance of 50 ohms
if the signal from an amplifier has an extremely low output impedance and an average output of 0V
if signal generator have an output coupling capacitor
if the signal generator have a high output impedance so that the 50 ohms load here shorts its signal
Please Sir..... This is for understanding purpose

audioguru · Feb 13, 2012

dexterdev said:
Can you please explain for each case?
if signal generator has average DC output of 0V but an output impedance of 50 ohms

Then the 50 ohms of the signal generator and the 50 ohms from the power supply form a voltage divider and reduce the AC signal and the average DC output to 0.5V. The output will be a 0.5V signal riding on +0.5V so it will swing from 0V to +0.5V.

if the signal from an amplifier has an extremely low output impedance and an average output of 0V

Then the output will be a 1V AC signal with no DC.

if signal generator have an output coupling capacitor

Then the output signal will have an average DC voltage of +1V.

if the signal generator have a high output impedance so that the 50 ohms load here shorts its signal

Then the AC will be zero and the output will be +1VDC.

Please Sir.....

I was not knighted by the Queen of England so I am not a Sir, instead I am just a COOL DUDE! Sometimes my wife calls me a .... never mind.

Ratchit · Feb 13, 2012

dexterdev,

You said in your previous post that the AC voltage source was "ideal". And since the AC source is grounded at the voltage reference point, point A is going to be the same as the output from the AC source, regardless of the value of the DC source.

Ratch

canadaelk · Feb 13, 2012

Let the OP do the simulation and learn! I'm just glad there are not 4 parts in this circuit! E

dexterdev · Feb 13, 2012

I got OP=original poster but what is E

Thankyou all for the replies

What is the output voltage in this circuit?

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