Math Problem Statement

Determine the resistor values (R, R_Ref, R_B) in a reference voltage circuit using semiconductor parameters such as V_BE, V_T, and the bandgap voltage V_GO.

Solution

The image appears to contain a set of calculations regarding a circuit or system design, possibly for a reference voltage circuit involving transistors or semiconductor components, as it refers to VBE (base-emitter voltage) and VT (thermal voltage). Here's a breakdown of the key equations and steps mentioned:

  1. Initial Equations:

    • I2=I1=VTln(n)R+VBERBI_2 = I_1 = \frac{V_T \ln(n)}{R} + \frac{V_{BE}}{R_B}
    • VRef=RRef×IV_{\text{Ref}} = R_{\text{Ref}} \times I
    • This is a general setup for finding reference voltages and currents using resistors RRefR_{\text{Ref}}, RBR_B, and using known parameters like VBEV_{BE}, the base-emitter voltage.
  2. Assumptions and Given Values:

    • Current I=15μAI = 15 \, \mu A
    • Number of diodes n=8n = 8
    • VBE=730mV,VT=26mVV_{BE} = 730 \, \text{mV}, \, V_T = 26 \, \text{mV} These values are standard for semiconductor analysis, especially for silicon-based circuits.
  3. Steps of Calculation:

    • After substitution into equations:
      • First, solving for RRefR_{\text{Ref}} leads to RRef=33.33kΩR_{\text{Ref}} = 33.33 \, k\Omega.
    • Substituting this back into the second equation leads to an expression for RBR_B, and further using values from Dr. Banba's paper, the final calculation yields:
      • RB=83.325kΩR_B = 83.325 \, k\Omega
    • Finally, calculating the resistor RR from the equation leads to R=8.66kΩR = 8.66 \, k\Omega.
  4. Final Notes:

    • The values RRefR_{\text{Ref}}, RBR_B, and RR are adjustable depending on specific design requirements or tuning.
    • VGOV_{GO}, the bandgap voltage of silicon extrapolated to absolute zero Kelvin, is used in the analysis. This is often around 1.25 V.

Would you like further details on any specific part of these calculations, or clarification on the steps?

Here are five questions you could explore to deepen understanding:

  1. What is the role of the thermal voltage VTV_T in the design of circuits like this?
  2. How do variations in VBEV_{BE} impact the calculation of RBR_B and RRefR_{\text{Ref}}?
  3. Why is the bandgap voltage VGOV_{GO} important in semiconductor circuits?
  4. How would adjusting the current II influence the resulting resistor values in the circuit?
  5. What is the significance of choosing n=8n = 8 diodes in this design?

Tip: When designing reference circuits, make sure to factor in temperature variations as they can significantly impact the performance of the components involved, particularly VBEV_{BE} and VTV_T.

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Math Problem Analysis

Mathematical Concepts

Circuit Analysis
Semiconductor Physics
Ohm's Law
Logarithmic Functions

Formulas

I_2 = I_1 = (V_T * ln(n) / R) + (V_BE / R_B)
V_Ref = R_Ref * I
R_B = (R_Ref / 500m) * 1.25
V_Ref = (R_Ref / R_B) * V_GO

Theorems

Bandgap Voltage Theorem (V_GO)
Exponential Behavior of Semiconductor Junctions

Suitable Grade Level

Undergraduate Level (Electrical Engineering)