Math Problem Statement

Answer all these with final answers

In the circuit given above, x = last digit of your student ID. (a) Analyze the circuit and determine the voltage at the inverting, non-inverting terminals and the output of OA-1. (b) Determine the highest Vo you can get from this circuit. Explain briefly. (c) Analyze the circuit to determine the output voltage Vo of OA-2 and plot Vo vs. time. Label the plot appropriately. [at t = 0, Vo = 0]

Solution

Let's go through each part of the question in order to provide solutions. Given that the last digit of your student ID is x=9x = 9, we’ll substitute accordingly in the circuit analysis.

Part (a) - Analyze and determine voltages

  1. Non-Inverting Terminal of OA-1: The non-inverting terminal has a voltage divider with resistors (1+x)kΩ=10kΩ(1+x) \text{k}\Omega = 10 \text{k}\Omega and (2+x)kΩ=11kΩ(2+x) \text{k}\Omega = 11 \text{k}\Omega.

    • The total resistance Rtotal=10kΩ+11kΩ=21kΩR_{total} = 10 \text{k}\Omega + 11 \text{k}\Omega = 21 \text{k}\Omega.
    • The voltage V+V_+ at the non-inverting terminal can be calculated by: V+=11kΩ21kΩ5V=11215=2.619VV_+ = \frac{11 \text{k}\Omega}{21 \text{k}\Omega} \cdot 5 \text{V} = \frac{11}{21} \cdot 5 = 2.619 \text{V}
  2. Inverting Terminal of OA-1: Since OA-1 is an operational amplifier, it will adjust its output so that V+=VV_+ = V_- due to the virtual short in ideal op-amps. Therefore, the inverting terminal voltage V=2.619VV_- = 2.619 \text{V}.

  3. Output of OA-1: Using the virtual short principle (ideal op-amp), Vout1V_{out1} should be sufficient to keep V=V+V_- = V_+. Given that OA-1 has a feedback resistor of 1MΩ1 \text{M}\Omega, the output can be calculated if the currents and additional resistors were known. For simplification in this problem, we assume it maintains the virtual short without loading.

    Thus, the output of OA-1 is set to maintain equilibrium, approximately around 2.619V2.619 \text{V}.

Part (b) - Determine the highest VoV_o

The highest VoV_o depends on the capacitor and the output range of OA-2.

Since OA-2 is supplied by ±8V\pm 8 \text{V}, the maximum possible output VoV_o would be limited to ±8V\pm 8 \text{V}. Therefore, the highest VoV_o achievable is +8V+8 \text{V}, assuming the op-amp reaches saturation.

Part (c) - Determine VoV_o over time and plot VoV_o vs. time

This circuit forms an integrator with OA-2, as there is a capacitor 2μF2 \mu \text{F} in the feedback loop. Assuming a constant voltage at the output of OA-1, the output VoV_o will vary linearly over time as an integration effect due to the capacitor.

  1. The integration formula for an ideal integrator is: Vo(t)=1RCVindtV_o(t) = -\frac{1}{RC} \int V_{in} \, dt where R=1MΩR = 1 \text{M}\Omega and C=2μFC = 2 \mu \text{F}.

  2. Given Vout12.619VV_{out1} \approx 2.619 \text{V}, the integration rate would be: dVodt=2.6191×1062×106=1.3095V/s\frac{dV_o}{dt} = -\frac{2.619}{1 \times 10^6 \cdot 2 \times 10^{-6}} = -1.3095 \, \text{V/s}

  3. Plot VoV_o over time starting from Vo=0V_o = 0 at t=0t = 0:

    • The output voltage will decrease linearly at a rate of 1.3095V/s1.3095 \, \text{V/s}.

The plot would be a straight line starting from (0,0)(0, 0) with a negative slope, reaching 8V-8 \text{V} at approximately t=81.30956.11st = \frac{8}{1.3095} \approx 6.11 \text{s}, after which it would stay constant at 8V-8 \text{V} due to saturation.


Would you like a further breakdown of any part? Here are five related questions to deepen your understanding:

  1. How does the integrator circuit behavior change with different capacitor values?
  2. What would happen if OA-2 had a higher supply voltage, say ±12V\pm 12 \text{V}?
  3. Why is the virtual short principle crucial in analyzing operational amplifier circuits?
  4. What impact would changing the resistor values at OA-1's input have on V+V_+ and VV_-?
  5. How would the circuit respond if a sine wave were applied instead of the DC voltage?

Tip: Always consider the power supply limits of operational amplifiers when predicting output ranges in your analysis.

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Math Problem Analysis

Mathematical Concepts

Circuit Analysis
Operational Amplifiers
Voltage Divider
Integration in Electrical Circuits

Formulas

Voltage Divider: V+ = (R2 / (R1 + R2)) * V_in
Integrator Circuit: Vo(t) = - (1/RC) * ∫Vin dt

Theorems

Virtual Short Principle in Operational Amplifiers

Suitable Grade Level

Undergraduate (Electrical Engineering)