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Q&A Calculating base voltage of NPN transistor

For my opinion, it is not too complicated to reduce the various equations to a system of two equations with two unknowns (current Ib2 neglected), Let me try: Vb1-Vx=I5*R5 I5=IC4+Vb1/R3 IC4=Ue...

posted 6mo ago by LvW‭  ·  edited 6mo ago by LvW‭

Answer
#3: Post edited by user avatar LvW‭ · 2024-05-12T14:23:24Z (6 months ago)
  • For my opinion, it is not too complicated to reduce the various equations to a system of two equations with two unknowns (current Ib2 neglected),
  • Let me try:
  • * Vb1-Vx=I5*R5
  • * I5=IC4+Vb1/R3
  • * IC4=Ue4/R4
  • * Ue4=VB2-0.7
  • These 4 equations (simple insertion procedure) result in:
  • * Vb1-Vx=R5[(Vb2-0.7)/R4 + Vb1/R3]
  • * Now we can Vb2 express as a function Vx (voltage division) and we have an equation with the **two unknowns Vb1 and Vx**.
  • * A **second equation for Vb1 and Vx** can be derived from
  • (V1-Vx)/R10=I10=I5+(Vx/Rx) with I5=(Vb1-Vx)/R5.
  • * The resistor Rx is the total resistance between Vx and ground.
  • For my opinion, it is not too complicated to reduce the various equations to a system of two equations with two unknowns (current Ib2 neglected),
  • Let me try:
  • * Vb1-Vx=I5*R5
  • * I5=IC4+Vb1/R3
  • * IC4=Ue4/R4
  • * Ue4=VB2-0.7
  • These 4 equations (simple insertion procedure) result in:
  • * Vb1-Vx=R5[(Vb2-0.7)/R4 + Vb1/R3]
  • * Now we can Vb2 express as a function Vx (voltage division) and we have an equation with the **two unknowns Vb1 and Vx**.
  • * A **second equation for Vb1 and Vx** can be derived from
  • (V1-Vx)/R10=I10=I5+(Vx/Rx) with I5=(Vb1-Vx)/R5.
  • * The resistor Rx is the total resistance between Vx and ground.
  • * Last step: Solve the system with two equations for two unknowns.
#2: Post edited by user avatar LvW‭ · 2024-05-12T14:21:48Z (6 months ago)
  • For my opinion, it is not too complicated to reduce the various equations to a system of two equations with two unknown (Current Ib2 neglected),
  • Let me try:
  • * Vb1-Vx=I5*R5
  • * I5=IC4+Vb1/R3
  • * IC4=Ue4/R4
  • * Ue4=VB2-0.7
  • These 4 equations (simple insertion procedure) result in:
  • * Vb1-Vx=R5[(Vb2-0.7)/R4 + Vb1/R3]
  • * Now we can Vb2 express as a function Vx (voltage division) and we have an equation with the **two unknowns Vb1 and Vx**.
  • * A **second equation for Vb1 and Vx** can be derived from
  • (V1-Vx)/R10=I10=I5+(Vx/Rx) with I5=(Vb1-Vx)/R5.
  • * The resistor Rx is the total resistance between Vx and ground.
  • For my opinion, it is not too complicated to reduce the various equations to a system of two equations with two unknowns (current Ib2 neglected),
  • Let me try:
  • * Vb1-Vx=I5*R5
  • * I5=IC4+Vb1/R3
  • * IC4=Ue4/R4
  • * Ue4=VB2-0.7
  • These 4 equations (simple insertion procedure) result in:
  • * Vb1-Vx=R5[(Vb2-0.7)/R4 + Vb1/R3]
  • * Now we can Vb2 express as a function Vx (voltage division) and we have an equation with the **two unknowns Vb1 and Vx**.
  • * A **second equation for Vb1 and Vx** can be derived from
  • (V1-Vx)/R10=I10=I5+(Vx/Rx) with I5=(Vb1-Vx)/R5.
  • * The resistor Rx is the total resistance between Vx and ground.
#1: Initial revision by user avatar LvW‭ · 2024-05-12T14:21:09Z (6 months ago)
For my opinion, it is not too complicated to reduce the various equations to a system of two equations with two unknown (Current Ib2 neglected),
Let me try:

* Vb1-Vx=I5*R5
* I5=IC4+Vb1/R3
* IC4=Ue4/R4
* Ue4=VB2-0.7

These 4 equations (simple insertion procedure) result in:

* Vb1-Vx=R5[(Vb2-0.7)/R4 + Vb1/R3]
* Now we can Vb2 express as a function Vx (voltage division) and we have an equation with the **two unknowns Vb1 and Vx**.

* A **second equation for Vb1 and Vx** can be derived from 
(V1-Vx)/R10=I10=I5+(Vx/Rx) with I5=(Vb1-Vx)/R5.
* The resistor Rx is the total resistance between Vx and ground.