Solving Circuits

davidand

Joined Jun 2, 2005
43
[attachmentid=685][attachmentid=686][attachmentid=687]Can someone point me in the right direction,
I attached a few homework problems I'm looking for some advice maybe someone can pass along or recommend a good book or web site to help me learn more about electronics.

hgmjr

Joined Jan 28, 2005
9,029
If you haven't already done so, take a look at the material contained in the tutorials on this website. There is some very good basic information available. Well worth the read.

hgmjr

davidand

Joined Jun 2, 2005
43
Originally posted by hgmjr@Jun 3 2005, 06:55 PM
If you haven't already done so, take a look at the material contained in the tutorials on this website. There is some very good basic information available. Well worth the read.

hgmjr
[post=8198]Quoted post[/post]​

I've been going through the tutorials,
I tried to solve HW 3 and I come up with R=0.564 ohms.
using 11.3/20.
Am I going in the right direction?

hgmjr

Joined Jan 28, 2005
9,029
Originally posted by davidand@Jun 3 2005, 06:24 PM
I've been going through the tutorials,
I tried to solve HW 3 and I come up with R=0.564 ohms.
using 11.3/20.
Am I going in the right direction?
[post=8200]Quoted post[/post]​
You are very close. The only thing you overlooked is that the current is 0.020 Amps rather than 20 amps. If you make that adjustment you will be right on the money.

hgmjr

davidand

Joined Jun 2, 2005
43
Originally posted by hgmjr@Jun 3 2005, 07:31 PM
You are very close. The only thing you overlooked is that the current is 0.020 Amps rather than 20 amps. If you make that adjustment you will be right on the money.

hgmjr
[post=8201]Quoted post[/post]​
Thanks
I'm tryng HW#2 now
so far I have V
B = 7.9V

hgmjr

Joined Jan 28, 2005
9,029
Originally posted by davidand@Jun 4 2005, 12:42 PM
Thanks
I'm tryng HW#2 now
so far I have V
B  = 7.9V
[post=8209]Quoted post[/post]​
I believe you need to take another look at your work in calculating Vb.

HW#2(hint)
The three diodes play a key role in the setting the value of Vb.

One important parameter appears to be absent from the definition for HW#2 problem. I am surprised that the transistor's beta is not part of the set of givens for the problem.

HW#1(observation)
Is it possible that the circuit node where the 430 ohm emitter resistor and the 5V zener diode's anode are connected is also tied to a source of negative voltage that is not shown?

hgmjr

davidand

Joined Jun 2, 2005
43
Originally posted by hgmjr@Jun 4 2005, 02:17 PM
I believe you need to take another look at your work in calculating Vb.

HW#2(hint)
The three diodes play a key role in the setting the value of Vb.

One important parameter appears to be absent from the definition for HW#2 problem. I am surprised that the transistor's beta is not part of the set of givens for the problem.

HW#1(observation)
Is it possible that the circuit node where the 430 ohm emitter resistor and the 5V zener diode's anode are connected is also tied to a source of negative voltage that is not shown?

hgmjr
[post=8211]Quoted post[/post]​
Your correct for HW #1 I went online with instructor and he gave me the corrected
HW#1.

For HW#2 I did subtract 0.7 for each diode. I'm researching the chapter on diodes now.

Thanks for you input.

hgmjr

Joined Jan 28, 2005
9,029
Hi davidand,

I think that there may be some information missing on the figure for HW#2. Is it possible that the circuit node associated with the cathode of the bottom diode and the bottom leg of the 15 ohm emitter resistor is attached to a negative power source?

I made the assumption that the node was connected to ground based on the figure. That may be why I did not get the same answer that you did.

Once this question is cleared up I think you are on the right track.

I am guessing that the node in question is tied to -10V. Am I right?

You're doing pretty good so far.

hgmjr

davidand

Joined Jun 2, 2005
43
Originally posted by hgmjr@Jun 4 2005, 07:41 PM
Hi davidand,

I think that there may be some information missing on the figure for HW#2. Is it possible that the circuit node associated with the cathode of the bottom diode and the bottom leg of the 15 ohm emitter resistor is attached to a negative power source?

I made the assumption that the node was connected to ground based on the figure. That may be why I did not get the same answer that you did.

Once this question is cleared up I think you are on the right track.

I am guessing that the node in question is tied to -10V. Am I right?

You're doing pretty good so far.

hgmjr
[post=8213]Quoted post[/post]​
Yes it is connected to -10V

hgmjr

Joined Jan 28, 2005
9,029
Originally posted by davidand@Jun 4 2005, 12:42 PM
Thanks
I'm tryng HW#2 now
so far I have VB  = 7.9V
[post=8209]Quoted post[/post]​
Now that I have the missing piece of information from HW#2, I can see where you got your answer.

Suggest you take a second look at the sign of your result. Keep in mind that the diodes are referenced to the -10V.

hgmjr

davidand

Joined Jun 2, 2005
43
Originally posted by hgmjr@Jun 4 2005, 08:10 PM
Now that I have the missing piece of information from HW#2, I can see where you got your answer.

Suggest you take a second look at the sign of your result. Keep in mind that the diodes are referenced to the -10V.

hgmjr
[post=8215]Quoted post[/post]​

thanks hgmij
The book I'm using id a reprint for Bura of Navy,
I'm taking a distance learning course and this is a reference book, it's pretty basic
I'm trying to find a book on solving circuits.
I'm still trying.
again thanks

davidand

Joined Jun 2, 2005
43
Originally posted by JoeJester@Jun 5 2005, 06:15 PM
What is the navedtra number on that book? What is the title to that book?
[post=8238]Quoted post[/post]​
I will get that info to you soon, I left book at work.
I'll post info soon.

davidand

Joined Jun 2, 2005
43
Originally posted by hgmjr@Jun 4 2005, 08:10 PM
Now that I have the missing piece of information from HW#2, I can see where you got your answer.

Suggest you take a second look at the sign of your result.  Keep in mind that the diodes are referenced to the -10V.

hgmjr
[post=8215]Quoted post[/post]​
For HW#2
I find
V
B = -7.9

V
C = 0

V
E =0

I use the following

V
C = 10V - (IR)

It does'nt look right can someone check this and explain it to me?

hgmjr

Joined Jan 28, 2005
9,029
Originally posted by davidand@Jun 7 2005, 10:09 AM
For HW#2
I find
V
B = -7.9

V
C = 0

V
E =0

I use the following

V
C = 10V - (IR)

It does'nt look right can someone check this and explain it to me?
[post=8287]Quoted post[/post]​

You need to take a second look at your Vc and Ve calculations.

HINT: The voltage at the emitter will be more negative than the voltage at the base. Keep in mind that you are dealing with an NPN silicon transistor.

Once you have Ve then you will have most of what you need to calculate Vc. Since you have no value for the beta of the transistor we will be forced to assume a value of say 100. That is unless you know the actual value posed by the problem. Or we can assume that Ie is equal to Ic and proceed on that basis.

Hang in there.
hgmjr

davidand

Joined Jun 2, 2005
43
Originally posted by JoeJester@Jun 5 2005, 06:15 PM
What is the navedtra number on that book? What is the title to that book?
[post=8238]Quoted post[/post]​
NAVPERS 10087-C
Basic Electronics

I bought it at Barnes +Noble

I'm in Army All the manuals for electronics courses are made advailable for me
but no hard copy I must download them and print it if I want hard copy.
Cheaper to buy the book for \$14.95

davidand

Joined Jun 2, 2005
43
Originally posted by hgmjr@Jun 7 2005, 12:14 PM

You need to take a second look at your Vc and Ve calculations.

HINT: The voltage at the emitter will be more negative than the voltage at the base. Keep in mind that you are dealing with an NPN silicon transistor.

Once you have Ve then you will have most of what you need to calculate Vc. Since you have no value for the beta of the transistor we will be forced to assume a value of say 100. That is unless you know the actual value posed by the problem. Or we can assume that Ie is equal to Ic and proceed on that basis.

Hang in there.
hgmjr
[post=8289]Quoted post[/post]​
I worked HW#2 some more

V
B = -7.9V

V
E = -8.6V

V
C = 24.4V

hgmjr

Joined Jan 28, 2005
9,029
Originally posted by davidand@Jun 8 2005, 08:55 AM
I worked HW#2 some more

V
B = -7.9V

V
E = -8.6V

V
C = 24.4V
[post=8318]Quoted post[/post]​
Your value for Ve is now correct.

Your value for Vc is off. I think I can understand where you made the error.

HINT: The value of the emitter current is computed by the voltage "drop" across the emitter resistor.

I think what you may have done is used the value of Ve directly in your calculation of the current flowing in the emitter resistor.

HINT: In the transistor stage of HW#2, any computed voltage that is more positive than the positive power supply or more negative than your negative supply should be view with suspicion.

Still you are making progress.

hgmjr

davidand

Joined Jun 2, 2005
43
Originally posted by hgmjr@Jun 8 2005, 10:51 AM
Your value for Ve is now correct.

Your value for Vc is off. I think I can understand where you made the error.

HINT: The value of the emitter current is computed by the voltage "drop" across the emitter resistor.

I think what you may have done is used the value of Ve directly in your calculation of the current flowing in the emitter resistor.

HINT: In the transistor stage of HW#2, any computed voltage that is more positive than the positive power supply or more negative than your negative supply should be view with suspicion.

Still you are making progress.

hgmjr
[post=8319]Quoted post[/post]​
I calculate it to be 9.96V now.

hgmjr

Joined Jan 28, 2005
9,029
Originally posted by davidand@Jun 8 2005, 06:19 PM
I calculate it to be 9.96V now.
[post=8332]Quoted post[/post]​
That is still not quite it.

What value do you get for the emitter current?

hgmjr

davidand

Joined Jun 2, 2005
43
Originally posted by hgmjr@Jun 8 2005, 07:22 PM
That is still not quite it.

What value do you get for the emitter current?

hgmjr
[post=8333]Quoted post[/post]​
-8.6V/15 Ω =0.57mA

10V-(0.57)(60 Ω )=9.49V