wow, that will end up in an huge train of equation... I tried to do it using the the usual result for that parallel and probably, your short for the parallel result will probably work better!
Differential Amplifier circuit
- Thread starter PsySc0rpi0n
- Start date
wow, that will end up in an huge train of equation... I tried to do it using the the usual result for that parallel and probably, your short for the parallel result will probably work better!
I got this:
\(\displaystyle {\frac{\left [ V_{x}\cdot \left ( hie+R_{y} \right )\cdot r_{o}\cdot R_{E} \right ]\cdot \left ( R_{E}+hie+R_{y} \right )}{\left [ r_{o}\cdot \left ( hfe+1 \right )\cdot r_{o}\cdot R_{E}+\left ( hie+R_{y} \right )\cdot \left ( R_{E} +r_{o}\right ) \right ]\cdot R_{E}\cdot \left ( hie+R_{y} \right )}}\)
\(\displaystyle {\frac{\left [ V_{x}\cdot \left ( hie+R_{y} \right )\cdot r_{o}\cdot R_{E} \right ]\cdot \left ( R_{E}+hie+R_{y} \right )}{\left [ r_{o}\cdot \left ( hfe+1 \right )\cdot r_{o}\cdot R_{E}+\left ( hie+R_{y} \right )\cdot \left ( R_{E} +r_{o}\right ) \right ]\cdot R_{E}\cdot \left ( hie+R_{y} \right )}}\)
Bordodynov
- Joined May 20, 2015
- 3,181
I see heaps of formulas, in order to obtain more accurate results. But if the precise formulas are substituted inaccurate data, the result is inaccurate. Once again, that "beta" does not equal "BF". "BF" Spice is an option. Just perfect for the transistor are equal. Gain coefficients everything else depends on the parameters:
is=14.34f xti=3 eg=1.11 vaf=74.03 bf=255.9 ne=1.307 ise=14.34f ikf=.2847 xtb=1.5
The gain depends on the operation mode.
I have given the scheme for calculating the coefficients using LTspice: Beta_dc and Beta_ac.
is=14.34f xti=3 eg=1.11 vaf=74.03 bf=255.9 ne=1.307 ise=14.34f ikf=.2847 xtb=1.5
The gain depends on the operation mode.
I have given the scheme for calculating the coefficients using LTspice: Beta_dc and Beta_ac.
@Jony130 I'll deal with the equation later! I'm at work and without time now!
Ok, I'll have that in mind... but somehow all the previous calcs have been close to LTSpice. But that's not the most important. The most important is the process of evaluating the symbolic formulas!
The Electrician
- Joined Oct 9, 2007
- 2,970
What's the problem? Looks to me like it's just fine. Set ro=100000 to get the same results I got earlier.
I think my previous equation, at post #102, is the same but @Jony130 said that I should review my calcs...
The Electrician
- Joined Oct 9, 2007
- 2,970
The reason he said that is because it doesn't give the same result:
Your expression in post #106 gives the correct result.
Bordodynov
- Joined May 20, 2015
- 3,181
Ro=VAF/ic ==> Ro=VAF/icq4=74.03V/4.203mA=17.61kOhm=17610,
hie=25.8e-3/4.226e-3*(255+1) = 1562.896 !
LTspice ==> Rout_Current=489.44kOm Beta_Acq4=188.7 hie4=25.8e-3/4.226e-3*(188.7+1) =1158.13
Beta_Acq4=178.06799 hie3=25.8e-3/4.226e-3*(178.06799+1) =1093.22
hie=25.8e-3/4.226e-3*(255+1) = 1562.896 !
LTspice ==> Rout_Current=489.44kOm Beta_Acq4=188.7 hie4=25.8e-3/4.226e-3*(188.7+1) =1158.13
Beta_Acq4=178.06799 hie3=25.8e-3/4.226e-3*(178.06799+1) =1093.22
Morning @The Electrician and @Bordodynov ... Thanks for your help...
Once my equation is correct, I'll keep going with the calcs!
Once my equation is correct, I'll keep going with the calcs!
I'm not getting the same result... Notice that the 'ro' of the denominator is multiplying by the whole denominator! I'm not sure if your result is taking that detail into account!
I'm getting 1.6 MΩ
I just did a small script in Octave to make things easier...
Code:
Re4=200;
hie=3000;
hfe=255;
ro=100e3;
Ry = 192;
Rp = 1/((1/Re4)+(1/(Re4 + hie)))
Ry=192
Ve = (ro*Re4*(hie+Ry))/(ro*((hfe+1)*ro*Re4+(hie+Ry)*(Re4+ro)))
Ix = Ve/Rp
Rx = 1/Ix
Ix1 = (ro*Re4*(hie+Re4)*(hie+Re4+Ry))/(Re4*(hie+Ry)*ro*((hfe+1)*ro*Re4+(hie+Ry)*(Re4+ro)))
Last edited:
The Electrician
- Joined Oct 9, 2007
- 2,970
Look closely. I am multiplying the entire denominator by ro.
It appears you made a small mistake line 8 as shown in red:
Ve = (ro*Re4*(hie+Ry))/(ro*((hie+1)*ro*Re4+(hie+Ry)*(Re4+ro)))
You should be getting 1.6 megohms, as I showed in post #107
Last edited:
Yeah, already corrected it at line 8.
Yes, I'm getting 1.6 MΩ, sharp...
But what is the difference between your post #107 and #109???
Yes, I'm getting 1.6 MΩ, sharp...
But what is the difference between your post #107 and #109???
The Electrician
- Joined Oct 9, 2007
- 2,970
My post #109 is testing your formula from your post #102, which gives a wrong result.
Ah ok... My result is 1.6 MΩ and your is 1.6039689 MΩ. It's yet 4kΩ of difference... Wonder if this is a significant difference! Maybe it's because you used the exact value of Ry which was a bit lower than what I used... Like 191.... Ω against the vale I used of 192 Ω
Bordodynov
- Joined May 20, 2015
- 3,181
Morning
I am sorry.
Beta_Acq3=178.06799 It is this value should be taken for the calculations. If you take the Beta_Acq4, will double, depending on the accounting (Ic=F(beta,VAF,Vce))
I am sorry.
Beta_Acq3=178.06799 It is this value should be taken for the calculations. If you take the Beta_Acq4, will double, depending on the accounting (Ic=F(beta,VAF,Vce))
Ok, thanks for your calcs!
The Electrician
- Joined Oct 9, 2007
- 2,970
I'm sure that's the difference.
Well, after running the circuit with the current mirror in LTSpice, somehow the Adm is half of what was before... Why is that?
From calcs I got pretty much the same, but LTSpice shows half of the Adm against the version without the current mirror!
9.6 V-1.3 V = 8.3 V
8.3 V / 2 = 4.15 V
Adm = Vo/Vi = 4.15 V / 0.45 V = 9.22
It should be around 18.
Not sure what is happening!
Edited;
Will it be due to the fact that I'm using Voc1 with respect to GND and not with respect to Voc2???
From calcs I got pretty much the same, but LTSpice shows half of the Adm against the version without the current mirror!
9.6 V-1.3 V = 8.3 V
8.3 V / 2 = 4.15 V
Adm = Vo/Vi = 4.15 V / 0.45 V = 9.22
It should be around 18.
Not sure what is happening!
Edited;
Will it be due to the fact that I'm using Voc1 with respect to GND and not with respect to Voc2???
Attachments
Last edited:
