OK Try this circuit:

View attachment 194092

Assume β = 100 and the circuit is "driven" from a ideal voltage source.

Av = ?

hmm...I missed it? \[ -16.2/5 \] is Av

 

If the circuit is "driven" from an ideal voltage source the gain will be equal to (20k||5k)/1k = 4V/V if we ignore re.
The RB will not be "reflected" at the emitter side due to the ideal voltage source driving the amplifier input.

 

If the circuit is "driven" from an ideal voltage source the gain will be equal to (20k||5k)/1k = 4V/V if we ignore re.
The RB will not be "reflected" at the emitter side due to the ideal voltage source driving the amplifier input.

yeah : was just thinking it..will be Rb || 0 = 0

Please another test..1 more

 

Please another test..1 more

Here you have

First circuit:



And the bonus circuit:

 

Here you have

First circuit:

View attachment 194102

And the bonus circuit:

View attachment 194103

first is -19.8....or you can say -20

2nd one not sure but will guess about -200 (doubt it)

 

first is -19.8....or you can say -20

Oki. but why 19.8? I would say 20.

2nd is about -200?

No, wrong, This one is a tricky.

 

Oki. but why 19.8? I would say 20.


No, wrong, This one is a tricky.

19.8 because of β/ (β+1)...20 if ratio is 1

Hmm okay...trying again..Thanks

The resistance in the current source is not important?

There is no gain? but attenuation?

 

The resistance in the current source is not important?

Assume ideal current source, hence ro = ∞

 

Assume ideal current source, hence ro = ∞

no gain then? is the answer a number?

 

Good job, no gain.

 

Good job, no gain.

lol aii...Need study my first circuit then read the links and see

Thanks

 

lol aii...Need study my first circuit then read the links and see

Exactly this is what you need to do now. And I have to go to sleep.

 

Exactly this is what you need to do now. And I have to go to sleep.

lol...Sleep well... hopefully you have a dream

 

I think there is an error(s) in the book.
First: No gain?? I think 330k should be 330 ohms. Now we have gain.
Second: Bias is not right, never was. 6.1k should be 61k
In SPICE I changes the 1V signal on input to 0.5V.
Now the circuit is just strange.

Now Ve2 is at 6.8V or about 1/2 of the 12V supply. That is good.
I think "Vo" is the output not Ve2. Also strange.
With a 0.5V signal in Vin we get Ve2=about 4V and VO=3V peak.

If I was making this amplifier: (note 0.33 ohms could be 0)
View attachment 194076

in post #12. Do you know how he did the model ".n NPN(BF = 99)? "

Thanks

Actually : think know mistake for dc analysis : trying

Assumed Ic = Ie
Vb is base voltage of transistor 1
Ve emitter of 2nd

\[ Vth = Vcc - 22k * (Vb-.7)/330 \]

\[ (Vcc-Vb)/6.2 = Vb + ((Vb-Ve)/10) + (Vb -.7)/33 \]
\[ (Ve/4.9) + (Vb-Ve)/10 = 100 * (Vth - .7 - Ve)/22 \]

Please what am I missing? or rather what did I get cos know missed everything
Answer not corresponding

Thanks thanks

 

in post #12. Do you know how he did the model ".n NPN(BF = 99)? "

hi Z,
In the LTS cmp folder you should find 'standard.bjt'

I have taken a clip of the 2N3904 transistor, BF is the 'Gain' of the transistor
E

C:\Users\ericg\Documents\LTspiceXVII\lib\cmp\standard.bjt

.model 2N3904_100 NPN(IS=1E-14 VAF=100 Bf=100 IKF=0.4 XTB=1.5 BR=4 CJC=4E-12 CJE=8E-12 RB=20 RC=0.1 RE=0.1 TR=250E-9 TF=350E-12 ITF=1 VTF=2 XTF=3 Vceo=40 Icrating=200m mfg=Philips)

.model 2N3904_200 NPN(IS=1E-14 VAF=100 Bf=200 IKF=0.4 XTB=1.5 BR=4 CJC=4E-12 CJE=8E-12 RB=20 RC=0.1 RE=0.1 TR=250E-9 TF=350E-12 ITF=1 VTF=2 XTF=3 Vceo=40 Icrating=200m mfg=Philips)

 

hi Z,
In the LTS cmp folder you should find 'standard.bjt'

I have taken a clip of the 2N3904 transistor, BF is the 'Gain' of the transistor
E

C:\Users\ericg\Documents\LTspiceXVII\lib\cmp\standard.bjt

.model 2N3904_100 NPN(IS=1E-14 VAF=100 Bf=100 IKF=0.4 XTB=1.5 BR=4 CJC=4E-12 CJE=8E-12 RB=20 RC=0.1 RE=0.1 TR=250E-9 TF=350E-12 ITF=1 VTF=2 XTF=3 Vceo=40 Icrating=200m mfg=Philips)

.model 2N3904_200 NPN(IS=1E-14 VAF=100 Bf=200 IKF=0.4 XTB=1.5 BR=4 CJC=4E-12 CJE=8E-12 RB=20 RC=0.1 RE=0.1 TR=250E-9 TF=350E-12 ITF=1 VTF=2 XTF=3 Vceo=40 Icrating=200m mfg=Philips)

Hmm E,
I do not understand...I found the folder and standard.bjt
nvm...thought could not edit

so can't change it in the simulator directly?

Also seeing TIP, Bc transistors but not available in the simulator

 

hi Z,
To edit the standard.bjt use a Text Editor.
I would advise you to make a copy of the standard.bjt BEFORE editing any of the components.
An easy way to check out different BF values for a transistor, is make a Copy and Paste of the transistors details.
Rename the Pasted copy
eg :
.model My_2N3904_100 NPN(IS=1E-14 VAF=100 Bf=100 IKF=0.4 XTB=1.5 BR=4 CJC=4E-12 CJE=8E-12 RB=20 RC=0.1 RE=0.1 TR=250E-9 TF=350E-12 ITF=1 VTF=2 XTF=3 Vceo=40 Icrating=200m mfg=Philips)
and Save the standard.bjt file.

To make that edited copy active, close down and restart LTSpice, the My_2N3904_100 should appear in the listing when using F2.

OK.?
E

Another quick fix way is to paste this into your circuit, it works but it looks messy IMO.

.model My_2N3904_100 NPN(IS=1E-14 VAF=100 Bf=100 IKF=0.4 XTB=1.5 BR=4 CJC=4E-12 CJE=8E-12 RB=20 RC=0.1 RE=0.1 TR=250E-9 TF=350E-12 ITF=1 VTF=2 XTF=3 Vceo=40 Icrating=200m mfg=Philips)

 

Another quick fix way is to paste this into your circuit, it works but it looks messy IMO.

.model My_2N3904_100 NPN(IS=1E-14 VAF=100 Bf=100 IKF=0.4 XTB=1.5 BR=4 CJC=4E-12 CJE=8E-12 RB=20 RC=0.1 RE=0.1 TR=250E-9 TF=350E-12 ITF=1 VTF=2 XTF=3 Vceo=40 Icrating=200m mfg=Philips)

Yeah the quick fix.. Unfortunately, still do not follow...Can do something like in the image below?

 

hi Z,
I have modified your original circuit to demo the BF option.
E
Note:
In order to Paste any text into a LTS circuit drawing.
Copy the text as usual from the Text Editor...
then Press 'S' on the keyboard, then paste the text into that Pop Up box.

 

hi Z,
I have modified your original circuit to demo the BF option.
E
Note:
In order to Paste any text into a LTS circuit drawing.
Copy the text as usual from the Text Editor...
then Press 'S' on the keyboard, then paste the text into that Pop Up box.

Thanks but how did you find it? The My_2n3904 ?

when you press F2? or after pressing F2 and choosing npn?

"

To make that edited copy active, close down and restart LTSpice, the My_2N3904_100 should appear in the listing when using F2."

not for me