# Solve for VL

#### davidand

Joined Jun 2, 2005
43
In the op amp circuit it asks for VL I use the V Ref from the zener am I missing something else to solve for VL?

#### davidand

Joined Jun 2, 2005
43
Originally posted by JoeJester@Jun 14 2005, 03:35 PM
davidand,

Both schematics are difficult to read. Did you get them out of a book?

To cut down on the file size, try saving them as gif or jpg.
[post=8497]Quoted post[/post]​

I'll try and redo the schenatics tomorrow,

I copied off blackboard and one was attached to an e-mail.

I was trying to determine to solve for V L when the zener was referencing 24V if there was a formula to solve for VL

#### davidand

Joined Jun 2, 2005
43
Originally posted by JoeJester@Jun 14 2005, 06:21 PM
David,

As far as your regulator goes, the opamp is operating as a voltage comparator. When the sample voltage [top of RL] exceeds the reference [the zener] Q1 stops conducting and when it drops below the reference, Q1 starts conducting. VL is approximately 24 volts.

What was the question on the other circuit?
[post=8500]Quoted post[/post]​

I'm tring to find quiescent drain current and voltage.

#### davidand

Joined Jun 2, 2005
43
Originally posted by JoeJester@Jun 14 2005, 07:28 PM
Ok ....

Here's what I think that second circuit looks like .... let me know where my errors are.
[post=8504]Quoted post[/post]​
Yes but the VGG polarity is backwards and the VDD = 20v

#### davidand

Joined Jun 2, 2005
43
R2 = 7k
What I'm looking for is if I'm given the drain current there are a lot of practice exercies where they give me the Q drain current and to find theQ drain voltage
in this example they give me 1mA drain current.

#### davidand

Joined Jun 2, 2005
43
I have been using VD = VDD -IDDS RD

20V-(1mA)(7k) = 13

#### davidand

Joined Jun 2, 2005
43
Originally posted by JoeJester@Jun 15 2005, 11:01 AM
20 - (1 mA * 7k) = 13 V

You are correct.

In my now deleted post, I didn't know of the additional information.

Are all these questions from a single reference?
[post=8527]Quoted post[/post]​

No I'm getting these problems from Army radar repair tech's. I'm trying to prepare myself for a future training course I may have to take.

I'm in the process of trying to learn the basic of electronics, for the course they use the Navy books as a reference.

So they keep changing things in the circuits so I can practice the basics.
thanks joe