- #1
bnosam
- 148
- 0
Homework Statement
http://i59.tinypic.com/1smqlu.png
I'm not sure how to calculate differential mode gain
Homework Equations
I know formuals for CMRR and Acm but not Adm
CMRR = | Adm/Acm |
Rb/Ra = (1-ε)Rd/Rc
Well let's see. You've used 1000 for R3 when the circuit says it's 24000. You've used 24000 for R4 when your circuit says it's 25000, and 25000 for R2 when your circuit gives it as 1000.bnosam said:So using:
Ad = 1/2[R3/(R1+R3)] [(R4 + R2)/R2 + R4/R2]
1/2[1000/(1000+1000)] * [(24000 + 25000)/1000 + 24000/25000] = 12.49
So it's exactly half of what the answer should be according to the answers up there? 24.98? Why does it have the 1/2 in front of it? Without it the answer would be 24.98 which would be correct...
Lucky you! I never had it so easy :)bnosam said:I remember my prof deriving this for us but he told us we don't need to know how to derive it?
I agree with your result. My calculation gives Ad=24.49bnosam said:My answer in post #5 seems to be off by .5. I can't spot anything that's wrong
LvW said:I agree with your result. My calculation gives Ad=24.49
EDIT: Sorry, I have to correct myself (calculatiuon error): The result is, in fact: Ad=24.98
You and your calculator must have a difference of opinion on the order operations implied by a given key sequence.bnosam said:Where did I mess up? I keep putting it in my calculator and getting it wrong haha
Yeah that was the issue, thank you :)gneill said:Hmm. I think perhaps the given formula may have suffered from careless algebra. I derived the expression myself and used that, obtaining the correct result. The expression I arrived at was:
$$A_{dm} = \frac{1}{2} \left[ \left( \frac{R3}{R1 + R3} \right) \left( \frac{R2 + R4}{R2} \right) + \frac{R4}{R2} \right] $$
Differential mode gain is a measure of how much the output voltage of a circuit changes in response to a change in the differential input voltage. It is typically expressed in decibels (dB) and is used to evaluate the performance of amplifiers and other electronic circuits.
CMRR stands for common mode rejection ratio. It is a measure of how well a circuit can reject common mode signals, or signals that are present on both input terminals. A higher CMRR indicates better performance in rejecting unwanted common mode signals.
Acm, or common mode gain, is calculated by dividing the output voltage by the common mode input voltage. It is also sometimes expressed as a ratio or in decibels.
Adm, or differential mode gain, is the gain of the circuit for differential signals. It is important because it indicates the level of amplification for the desired input signals and can help determine the overall performance of the circuit.
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