Amp Circuit help

G

gbc2001

New Member

• Jun 6, 2011

• #1

Hi, (first post be gentle)

As part of a potential interview I have been given this question..

Despite having a good google - I can't really started with the question..

here is the circuit

**broken link removed**

and here are the questions

What is the gain of amplifier U41B?
What is the circuit configuration of U41A?
What is the expected maximum voltage range at “DEMAND+”?
What digital command streams would you expect to be sent to this circuit?

my thoughts, circuit configuration - scaling adder and gain rf/r1

any pointers to get me going would be most appreciated, thanks

kenny

 

Last edited: Jun 6, 2011

audioguru

Well-Known Member

Most Helpful Member

• Jun 6, 2011

• #2

Since you posted a very fuzzy JPG file type for the schematic instead of a very clear PNG file type then we cannot see the important details.

 

Attachments

• fuzzy opamp schematic.PNG

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Last edited: Jun 6, 2011

G

gbc2001

New Member

• Jun 6, 2011

• #3

Ok I will try and post up a better image...

 

G

gbc2001

New Member

• Jun 7, 2011

• #4

unable to get a better jpeg of the circuit...

any pointers appreciated

thanks

 

audioguru

Well-Known Member

Most Helpful Member

• Jun 7, 2011

• #5

A JPEG or JPG file type is not used for schematics because it makes lines look very fuzzy. We use PDF, GIF or PNG file types which make a schematic extremely clear.

You cannot simply convert a fuzzy JPG schematic, instead you must save the original schematic as a clear file type. I frequently copy a very clear schematic useing the PRINT SCRN key then paste it into Microsoft Paint program, crop it then save it as a very clear PNG file type.

 

Attachments

• fuzzy JPG file type again.PNG

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Ian Rogers

User Extraordinaire

Forum Supporter

Most Helpful Member

• Jun 7, 2011

• #6

I managed to clean up the diagram a tiny bit in CS3 the resistor in question is a 3.6k, that gives an amplification of x3 of U41B, the differentials are 1:1. ( 2.2k and 2.2k )

 

audioguru

Well-Known Member

Most Helpful Member

• Jun 7, 2011

• #7

Ian Rogers said:

I managed to clean up the diagram a tiny bit in CS3 the resistor in question is a 3.6k, that gives an amplification of x3 of U41B, the differentials are 1:1. ( 2.2k and 2.2k )

Click to expand...

No.
The gain of an inverting opamp would be 3.6k/1.2k= 3.0.
But your opamp is non-inverting so its gain is 1 plus (3.6k/1.2k)= 4.0.

 

G

gbc2001

New Member

• Jun 7, 2011

• #8

ok I have the circuit diagram on a PDF, will try and convert that into a suitable file..

will post it later

Kenny

 

ericgibbs

Well-Known Member

Most Helpful Member

• Jun 7, 2011

• #9

hi Kenny,
You can post pdf files to the thread, use 'Go Advanced'

 

Grossel

Well-Known Member

• Jun 7, 2011

• #10

I join this:

Formatting schematics as jpg is bad, but is not the only reason for bad schematics. Also the image resolution is very important. In this case, it's not sure it's readable even if we got a straighten version.

MS paint is suggested. I have a even better one. Use FSIV to take screenshots and save drawings as 8 bit png's. I think no program can produce smaller png's (i have tested it against other graphic programs that saved png's).

 

Ian Rogers

User Extraordinaire

Forum Supporter

Most Helpful Member

• Jun 7, 2011

• #11

Cheers audio!! Two pairs of eyes is better than one... You're the op-amp man, its a long time since I played with op-amps.