Hi all, I wonder if you can help point me in the right direction.
I have had an assignment returned with one error to the following question about an amplifier circuit.
we are given the input voltage, the output voltage and a noise voltage.
We are required to find the Gain in Volts G=Vout/Vin this gave 3.9V
The gain in decibels = 20log10(3.9) = 11.8dB
Then we require the SNR, I worked this out as SNR= 20log10( Vout/V noise) =
in this case 20log10 (3.7/0.0023)=64dB.
I was following an example in my work book that states.
A 1.5v audio signal contains a noise component of 4.2mV. the Signal to Noise ratio is then : SNR=20log10(1.5V/4.2mV) = 51dB
This is the part I have wrong, the tutors comment are that I should calculate the noise (in dB) and add that to the signal (gain). this will give the signal to noise ratio.
For this I would work out the noise at 0.0023V to be -52dB then add this to the Gain in dB so -52+11.8dB= -42dB
Is this last part correct have I understood the tutors comments, so the SNR will be -42dB? its just a very different answer to how I thought it should be worked out.
I only need to correct this one small question but I have got myself a little confused. p.s I am a noob of the highest order so some of the equations still make my head hurt.
Any advice you can offer is very much appreciated.
I have had an assignment returned with one error to the following question about an amplifier circuit.
we are given the input voltage, the output voltage and a noise voltage.
We are required to find the Gain in Volts G=Vout/Vin this gave 3.9V
The gain in decibels = 20log10(3.9) = 11.8dB
Then we require the SNR, I worked this out as SNR= 20log10( Vout/V noise) =
in this case 20log10 (3.7/0.0023)=64dB.
I was following an example in my work book that states.
A 1.5v audio signal contains a noise component of 4.2mV. the Signal to Noise ratio is then : SNR=20log10(1.5V/4.2mV) = 51dB
This is the part I have wrong, the tutors comment are that I should calculate the noise (in dB) and add that to the signal (gain). this will give the signal to noise ratio.
For this I would work out the noise at 0.0023V to be -52dB then add this to the Gain in dB so -52+11.8dB= -42dB
Is this last part correct have I understood the tutors comments, so the SNR will be -42dB? its just a very different answer to how I thought it should be worked out.
I only need to correct this one small question but I have got myself a little confused. p.s I am a noob of the highest order so some of the equations still make my head hurt.
Any advice you can offer is very much appreciated.