Differential line receiver input stage

In summary, the conversation discusses the input stage of an AM26LS32 differential line receiver. The data sheet has a circuit diagram for the input stage, but the purpose of the 100K and 20K resistors is unclear. It is mentioned that the input stage resembles a push-pull output stage and that the resistors are used for input biasing. The conversation then moves on to discussing a simulation schematic and its relationship to the original input schematic. The conversation ends with a question about the tolerance of the resistors and a suggestion to measure them accurately and adjust the schematic accordingly. The response states that the tolerance is 1% and that adjusting the values would not be a problem.
  • #1
likephysics
636
2
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
 
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  • #2
likephysics said:
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.
 
  • #3
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.
 

Attachments

  • diff inp.pdf
    5.2 KB · Views: 220
  • #4
Anyone?
 
  • #5
likephysics said:
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?
 
  • #6
berkeman said:
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.
 
  • #7
What is the tolerance of your resistors? Can you measure them as accurately as possible and change the values in your schematic accordingly?
 
  • #8
skeptic2 said:
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%.
 

Related to Differential line receiver input stage

What is a differential line receiver input stage?

A differential line receiver input stage is a circuit that is used to convert a differential signal, which has two complementary signals, into a single-ended signal. It is commonly used in communication systems to improve signal quality and reduce noise.

What is the purpose of a differential line receiver input stage?

The main purpose of a differential line receiver input stage is to amplify and filter a differential signal to improve its quality and reduce noise. It also helps to convert the signal into a single-ended signal which is easier to process and use in other circuits.

How does a differential line receiver input stage work?

A differential line receiver input stage consists of two differential amplifiers that amplify the positive and negative signals of the differential input. The amplified signals are then combined and filtered to produce a single-ended output signal.

What are the advantages of using a differential line receiver input stage?

There are several advantages of using a differential line receiver input stage. It helps to improve signal quality by amplifying and filtering the differential signal. It also reduces noise, improves common-mode rejection, and increases the overall stability of the system.

What are the applications of a differential line receiver input stage?

A differential line receiver input stage is commonly used in communication systems, such as telecommunication, data communication, and audio systems. It is also used in measurement and control systems, where high-quality signal acquisition is essential.

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