Why is T2 removed in low signal circuit analysis?

In summary, the original circuit is incorrect as there is no valid biasing of the transistors. The T2 transistor can be removed when performing low signal analysis as it serves as a current mirror for T3. The T1 transistor also acts as a current source and T3 has infinite impedance for AC. The collector of T3 is the input voltage point and T1 defines the operating point of the JFET amplifier.
  • #1
Drao92
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  • #3
Sure
The DC source is above the T3 transistor and resistor, i forgot to draw it.
The problem i have is that i can't understand what parts of the circuit i have to remove when i move from DC analysis to AC analysis. Can you recommend me a book or some documentation which explains this because i couldn't find any.
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  • #4
Drao92 said:
Sure
The DC source is above the T3 transistor and resistor, i forgot to draw it.
The problem i have is that i can't understand what parts of the circuit i have to remove when i move from DC analysis to AC analysis. Can you recommend me a book or some documentation which explains this because i couldn't find any.
https://www.physicsforums.com/attachment.php?attachmentid=57846&stc=1&d=1365923347

What is the component connected below the base of T2? Maybe a Zener diode?

What class is this for, and what is the standard textbook? Most textbooks on standard transistor analysis should cover how to analyze this circuit...
 
  • #5
I study amplifiers. Yes, its a zener diode.
The standard textbook is not in english and it doesn't cover these things.I made these on seminars
Ill post another example.
So, the T2 and T3 transistors make a DC source and its a ground in AC, but i don't understand why the T1 transistor is a ground too. This is the problem i have.
After i make the AC circuit i have to calculate Vo/Vi, Rin, Rout, very easy but if i don't know how to make the AC circuit is useless .
https://www.physicsforums.com/attachment.php?attachmentid=57856&stc=1&d=1365959633
 

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  • #6
T3 is not a ground for AC. In fact, it's infinite impedance (theoretically) for AC. It's a source of dc current. A current source has infinite impedance. In fact, the collector of T3 is your input voltage point.

T1 is also a current source. The function of T2 is to mirror the current through its collector to the collector of T3. T1 defines the collector current for T2 and trerefore for T3 also. T3 defines the operating point of the grounded-gate JFET amplifier.
 

Related to Why is T2 removed in low signal circuit analysis?

1. What is low signal circuit analysis?

Low signal circuit analysis is a method used to analyze electronic circuits that operate with low voltage or current levels. It involves studying the behavior of electrical components and signals in a circuit to better understand its performance.

2. Why is low signal circuit analysis important?

Low signal circuit analysis is important because it allows us to accurately predict and improve the performance of electronic circuits that operate with low levels of voltage or current. This is particularly useful in designing sensitive devices such as medical equipment, sensors, and communication systems.

3. What are some common techniques used in low signal circuit analysis?

Some common techniques used in low signal circuit analysis include Kirchhoff's laws, Thevenin's theorem, and nodal analysis. These methods help to simplify complex circuits and analyze the behavior of individual components.

4. What are the challenges of low signal circuit analysis?

One of the main challenges of low signal circuit analysis is dealing with the effects of noise on the circuit. Since low signal circuits operate at low levels, even small amounts of noise can significantly impact their performance. Another challenge is accurately measuring and controlling the low signal levels without introducing additional noise.

5. How can low signal circuit analysis be applied in real-world applications?

Low signal circuit analysis has many practical applications in industries such as healthcare, telecommunications, and aerospace. It is used to design and optimize electronic devices for specific purposes, such as medical monitoring equipment, satellite communication systems, and sensitive sensors for measuring environmental conditions.

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