How do you design an op amp circuit?

[MRW]

This question is related to my question about AGC threshold amplifiers.
But I feel that it is a topic of its own.

In general, if you were designing the threshold amplifier in the
picture (http://tinypic.com/view/?pic=333cv43), what would your thought
process be?

I am familiar with basic circuit analysis techniques and op amp golden
rules, but I'm still not able to come up with my own design. I
especially get confuse when I see capacitors because I don't know if
its there for filtering or as some sort of signal delay / charging
mechanism or as some sort of compensation.

 

[Mikkel Lund]

MRW skrev:

This question is related to my question about AGC threshold amplifiers.
But I feel that it is a topic of its own.

In general, if you were designing the threshold amplifier in the
picture (http://tinypic.com/view/?pic=333cv43), what would your thought
process be?

I am familiar with basic circuit analysis techniques and op amp golden
rules, but I'm still not able to come up with my own design. I
especially get confuse when I see capacitors because I don't know if
its there for filtering or as some sort of signal delay / charging
mechanism or as some sort of compensation.

I don't understand the question. The circuit is designed, do you want an
analysis of the given circuit?

 

[MRW]

I don't understand the question. The circuit is designed, do you want an
analysis of the given circuit?

Hello Mikkel:

In general, if someone asked you to design a threshold amplifier, how
would you go about designing it?

I just got curious because I do not have any design experience and was
wondering how the experienced designer would handle it. I even got more
curious because I was reading Jack Smith's Modern Communications
Circuits book and he seems to approach it from a mathematical route
where he derives the necessary equations that describe the general
system block and then he designs a circuit to mimic the function of
each system block. I wish they thought us this in school.

 

[Stanislaw Flatto]

Hello Mikkel:

In general, if someone asked you to design a threshold amplifier, how
would you go about designing it?

I just got curious because I do not have any design experience and was
wondering how the experienced designer would handle it. I even got more
curious because I was reading Jack Smith's Modern Communications
Circuits book and he seems to approach it from a mathematical route
where he derives the necessary equations that describe the general
system block and then he designs a circuit to mimic the function of
each system block. I wish they thought us this in school.

In every design there is the 'hickup' in explaining to the technical
people "what bothers you".
Once clearly over this hump you devise hardware to solve this problem.
Takes time to reach this stage. Keep learning. Your solutions will
improve with experience and knowledge technical AND mathematical.

Have fun

Stanislaw.

 

[Eeyore]

Hello Mikkel:

In general, if someone asked you to design a threshold amplifier, how
would you go about designing it?

How did you arrive at the one in the link ?

I'm puzzled by R3, 4, 5, 6 btw. You could do the same thing with 2 resistors.


Graham

 

[Eeyore]

Hello Mikkel:

In general, if someone asked you to design a threshold amplifier, how
would you go about designing it?

I just got curious because I do not have any design experience and was
wondering how the experienced designer would handle it. I even got more
curious because I was reading Jack Smith's Modern Communications
Circuits book and he seems to approach it from a mathematical route
where he derives the necessary equations that describe the general
system block and then he designs a circuit to mimic the function of
each system block. I wish they thought us this in school.

Sounds wacky to me.

Even if you're not using 'building blocks' from someone else's book, most design
engineers have 101 standard circuits they can adapt to many situations.

Every once in a while you get a chance to be a bit more inventive but a heck of
a lot is really quite routine.

Graham

 

[MRW]

Even if you're not using 'building blocks' from someone else's book, most design
engineers have 101 standard circuits they can adapt to many situations.

101 standard circuits? Where can I get a copy of these circuits.

Every once in a while you get a chance to be a bit more inventive but a heck of
a lot is really quite routine.

I'm not there, yet. Eventually it'll be come a routine.

Graham

Thanks, Graham!

 

[John Popelish]

101 standard circuits? Where can I get a copy of these circuits.

(snip)

Here are some good basic opamp application notes from
National Semi9conductor that you might study:
http://www.national.com/an/AN/AN-20.pdf
http://www.national.com/an/AN/AN-31.pdf

Application note list:
http://www.national.com/appinfo/amps/0,2175,967,00.html

 

[MRW]

Thanks, John! I didn't have the first PDF, but I had the second PDF
since last year. I also have some op amp collections from TI.