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I am calculating the base current of transistor Q1. To simplify the circuit equations, I applied the Thévenin's theorem twice and converted V1, R1 and R2 into Vth and Rth, as shown in the image. ...
#4: Post edited
by
Lorenzo Donati
·
2023-08-09T21:13:22Z (9 months ago)
Corrected math.
- I am calculating the base current of transistor Q1. To simplify the circuit equations, I applied the Thévenin's theorem twice and converted V1, R1 and R2 into Vth and Rth, as shown in the image.
- <br>
- \[
- \begin{align}
- V_{th} &= V_1 \times (R_2/R_1+R_2)
- && &
- R_{th} &= R_1 \parallel R_2
- \\[1 em]
- V_{th2} &= V_{th} \times (R_7/R_{th}+R_3+R_7)
- && &
- R_{th2} &= R_7 \parallel (R_{th}+R_3)
- \\[1 em]
V_a &= \pu{0.7V} + I_b \times (h_{fe}+1) \times 200- \end{align}
- \]
- 
- I can accurately calculate $I_b = \pu{2.09 mA}$ by using Kirchoff's voltage law, but I'm getting an inaccurate value ($I_b= \pu{213 \mu A}$) by applying Thévenin's theorem.
- Is Thévenin's theorem being applied incorrectly for the circuit?
- I am calculating the base current of transistor Q1. To simplify the circuit equations, I applied the Thévenin's theorem twice and converted V1, R1 and R2 into Vth and Rth, as shown in the image.
- <br>
- \[
- \begin{align}
- V_{th} &= V_1 \times (R_2/R_1+R_2)
- && &
- R_{th} &= R_1 \parallel R_2
- \\[1 em]
- V_{th2} &= V_{th} \times (R_7/R_{th}+R_3+R_7)
- && &
- R_{th2} &= R_7 \parallel (R_{th}+R_3)
- \\[1 em]
- V_a &= \pu{0.7V} + I_b \times (h_{fe}+1) \times \pu{200\Omega}
- \end{align}
- \]
- 
- I can accurately calculate $I_b = \pu{2.09 mA}$ by using Kirchoff's voltage law, but I'm getting an inaccurate value ($I_b= \pu{213 \mu A}$) by applying Thévenin's theorem.
- Is Thévenin's theorem being applied incorrectly for the circuit?
#3: Post edited
by
Lorenzo Donati
·
2023-08-09T21:11:44Z (9 months ago)
Improved math formatting. Retagged.
I am calculating the base current of transistor Q1. To simplify the circuit equations, I applied the Thévenin's theorem twice and converted V1 and R1, R2 into Vth and Rth as shown in the image.Vth= V1x(R2/R1+R2) ; Rth =R1||R2Vth2= Vthx(R7/Rth+R3+R7) ; Rth2=R7||(Rth+R3)Va= 0.7 + Ib x (hfe+1)x200- 
I can accurately calculate the Ib = 2.09mA by using Kirchoff's Voltage law but getting inaccurate value ( Ib= 213uA ) by applying Thévenin's theorem.- Is Thévenin's theorem being applied incorrectly for the circuit?
Thanks in advance
- I am calculating the base current of transistor Q1. To simplify the circuit equations, I applied the Thévenin's theorem twice and converted V1, R1 and R2 into Vth and Rth, as shown in the image.
- <br>
- \[
- \begin{align}
- V_{th} &= V_1 \times (R_2/R_1+R_2)
- && &
- R_{th} &= R_1 \parallel R_2
- \\[1 em]
- V_{th2} &= V_{th} \times (R_7/R_{th}+R_3+R_7)
- && &
- R_{th2} &= R_7 \parallel (R_{th}+R_3)
- \\[1 em]
- V_a &= \pu{0.7V} + I_b \times (h_{fe}+1) \times 200
- \end{align}
- \]
- 
- I can accurately calculate $I_b = \pu{2.09 mA}$ by using Kirchoff's voltage law, but I'm getting an inaccurate value ($I_b= \pu{213 \mu A}$) by applying Thévenin's theorem.
- Is Thévenin's theorem being applied incorrectly for the circuit?
#2: Post edited
by
Lundin
·
2022-05-20T07:45:56Z (almost 2 years ago)
Spelling
Thevenins Theoram for Transistor Circuit
- Thévenins Theorem for Transistor Circuit
Hello All ,I am calculating the base current of transistor Q1. To simplify the circuit equations, I applied the Thevenin's theorem twice and converted V1 and R1, R2 into Vth and Rth as shown in the image.- Vth= V1x(R2/R1+R2) ; Rth =R1||R2
- Vth2= Vthx(R7/Rth+R3+R7) ; Rth2=R7||(Rth+R3)
- Va= 0.7 + Ib x (hfe+1)x200
- 
I can accurately calculate the Ib = 2.09mA by using Kirchoff's Voltage law but getting inaccurate value ( Ib= 213uA ) by applying the 'Thevenins Theoram'.Is the Thevenins Theoram being applied incorrectly for the circuit ?Thanks in Advance
- I am calculating the base current of transistor Q1. To simplify the circuit equations, I applied the Thévenin's theorem twice and converted V1 and R1, R2 into Vth and Rth as shown in the image.
- Vth= V1x(R2/R1+R2) ; Rth =R1||R2
- Vth2= Vthx(R7/Rth+R3+R7) ; Rth2=R7||(Rth+R3)
- Va= 0.7 + Ib x (hfe+1)x200
- 
- I can accurately calculate the Ib = 2.09mA by using Kirchoff's Voltage law but getting inaccurate value ( Ib= 213uA ) by applying Thévenin's theorem.
- Is Thévenin's theorem being applied incorrectly for the circuit?
- Thanks in advance
#1: Initial revision
by
kadamrohan16
·
2022-05-19T15:32:30Z (almost 2 years ago)
Thevenins Theoram for Transistor Circuit
Hello All , I am calculating the base current of transistor Q1. To simplify the circuit equations, I applied the Thevenin's theorem twice and converted V1 and R1, R2 into Vth and Rth as shown in the image. Vth= V1x(R2/R1+R2) ; Rth =R1||R2 Vth2= Vthx(R7/Rth+R3+R7) ; Rth2=R7||(Rth+R3) Va= 0.7 + Ib x (hfe+1)x200  I can accurately calculate the Ib = 2.09mA by using Kirchoff's Voltage law but getting inaccurate value ( Ib= 213uA ) by applying the 'Thevenins Theoram'. Is the Thevenins Theoram being applied incorrectly for the circuit ? Thanks in Advance