- #1
kl055
- 26
- 0
Homework Statement
Why is R_E in parallel with 1/g_m1?
I drew the small signal model but it does not make sense to me
Understanding why R_E is in parallel with g_m in a BJT
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SUMMARY
The discussion centers on the relationship between the emitter resistor (R_E) and the transconductance (g_m1) in a BJT small signal model. Participants clarify that R_E is in parallel with 1/g_m1 due to the voltage divider effect influenced by the Early voltage (V_A). The analysis assumes a high beta (β) value to simplify the circuit behavior, indicating that circuits dependent on β are less desirable. Key parameters such as r23 and V_A require definition for a complete understanding of the circuit dynamics.
PREREQUISITES- Understanding of BJT small signal models
- Familiarity with transconductance (g_m) and its implications
- Knowledge of Early voltage (V_A) and its role in circuit analysis
- Concept of voltage dividers in electrical circuits
- Study the impact of Early voltage (V_A) on BJT performance
- Learn about the significance of transconductance (g_m) in amplifier design
- Explore the effects of varying beta (β) on BJT circuits
- Investigate the role of voltage dividers in small signal analysis
Electrical engineering students, circuit designers, and anyone studying BJT amplifier configurations will benefit from this discussion.
Why is R_E in parallel with 1/g_m1?
I drew the small signal model but it does not make sense to me
- #2
kl055
- 26
- 0
I get that V_A is given by a voltage divider, but why is R_E in parallel with 1/g_m1?
- #3
rude man
Science Advisor
- 8,032
- 870
Q3 is just a diode so gm3 can't play a role.
What is r23? What is VA? You need to define some of these parameters. I assume gm = β but am not sure ...
I analyzed the circuit assuming β → ∞. Why? Because any circuit that is β-dependent is not a good circuit.
So I got what looks like your expression if gm → ∞. I know that's not what you are trying to find out - sorry.
What is r23? What is VA? You need to define some of these parameters. I assume gm = β but am not sure ...
I analyzed the circuit assuming β → ∞. Why? Because any circuit that is β-dependent is not a good circuit.
So I got what looks like your expression if gm → ∞. I know that's not what you are trying to find out - sorry.
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