Please see the edit.

A source is coupled to a diff-amplifier circuit as sown below:

enter image description here

The 10k R1 provides a path for base currents to return.

But Im confused about the loop taken by ib2.

For ib1 I can say it loops through A-->B-->C(GND)-->D-->E--F

Is this loop for ib1 correct?

Im confused about ib2's track

Does ib2 loop through F-->G-->C(GND)-->D-->E-->F

But this doesn't make sense because current cannot loop back to the same terminal.

I put those capital letters for nodes as A, B, C ect.

What is the correct track for ib2?


Let me ask this way:


simulate this circuit – Schematic created using CircuitLab

In the above conceptual schematics Rb providing return path.

What are the loops for the input bias currents in terms of nodes for ib1 and ib2? I named all nodes with capital letters. An answer would be like A-->B--> ect. easy to demonstrate.

  • \$\begingroup\$ Why don't you put it in a simulator and see the voltages on the nodes then you'll get your answer and you'll be able to analyse its performance. Several simulators are free. If it's a case of not wanting to undertake the learning exercise for a sim then I'd say you are doing yourself a disservice. \$\endgroup\$ – Andy aka Mar 22 '18 at 15:30
  • \$\begingroup\$ I can sim in LTspice but it is not possible to track le courant particulier. I only need to see the actual ib1 and ib2. If it is possible I would be very glad if you tell me how. \$\endgroup\$ – user1245 Mar 22 '18 at 16:18
  • \$\begingroup\$ I opened a new question regarding the same schematics but different question: electronics.stackexchange.com/questions/364065/… Hope you have an input. \$\endgroup\$ – user1245 Mar 22 '18 at 17:16

Regarding second diagram:

path of ib2: BAT2(+)-> D -> Rb -> X/K -> B -> C -> BAT2(-);

path of ib1: BAT2(+)-> D -> Rb -> X -> A -> B -> C -> BAT2(-);

|improve this answer|||||
  • \$\begingroup\$ Sorry my mistake I named two different nodes nodes D. now I changed one as X please see the diagram again. Could you update your answer with the new letter X. It was my stupidity to name both D. \$\endgroup\$ – user1245 Mar 22 '18 at 16:24

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