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likephysics
Jun3-11, 05:26 AM
I was going thu AM26LS32 diff line receiver. The data sheet has a ckt diagram for the input stage. But I don't understand it.
I have attached the input stage from datasheet(page3)
The input stage actually looks like a push pull output stage.
What is the function of the 100K resistors and the 20K resistor.

http://images.elektroda.net/95_1307096582.jpg
berkeman
Jun3-11, 01:00 PM
I was going thu AM26LS32 diff line receiver. The data sheet has a ckt diagram for the input stage. But I don't understand it.
I have attached the input stage from datasheet(page3)
The input stage actually looks like a push pull output stage.
What is the function of the 100K resistors and the 20K resistor.

http://images.elektroda.net/95_1307096582.jpg

That's just the input bias portion of the receiver inputs. It looks like they are biasing the A and B inputs to slightly above and below (respectively) mid-rail.
likephysics
Jun8-11, 04:11 AM
I hooked up a circuit with a voltage divider at the input.
The differential input signal at the input of the diff receiver has a DC offset of 300mV when input is 5V square wave.
A small dc current (~40uA) is actually flowing out of the diff receiver input pins.
It doesn't make sense.
Is the bias being changed some how?
See attached pdf for ckt.
likephysics
Jun10-11, 09:51 AM
Anyone?
berkeman
Jun10-11, 11:49 AM
I hooked up a circuit with a voltage divider at the input.
The differential input signal at the input of the diff receiver has a DC offset of 300mV when input is 5V square wave.
A small dc current (~40uA) is actually flowing out of the diff receiver input pins.
It doesn't make sense.
Is the bias being changed some how?
See attached pdf for ckt.

Sorry, what is the relationship of the simulation schematic in this PDF to the original input schematic in your first post?
likephysics
Jun12-11, 05:02 AM
Sorry, what is the relationship of the simulation schematic in this PDF to the original input schematic in your first post?
The PDF is just to give you an idea of the ckt.
skeptic2
Jun12-11, 08:03 AM
What is the tolerance of your resistors? Can you measure them as accurately as possible and change the values in your schematic accordingly?
likephysics
Jun13-11, 12:28 PM
What is the tolerance of your resistors? Can you measure them as accurately as possible and change the values in your schematic accordingly?

Sure, that wouldn't be a problem.

The tolerance is 1%.