Electronics 2 - Homework 2 Second semester 2023-2024 Solve the following questions, and verify your solution using LTSpice. simulation. For each question you need to:Solve the question by handProvide a screenshot of the circuitProvide a screenshot confirming the hand calculations Note that you can change the BJT parameter Beta by adding a SPICE directive and changing the parameter BF Question 1: BJT transistors The parameters for each transistor in the figure below are β = 80, and VBE(m) = 0.7 V. Determine all the voltages and currents in the circuit. Circuit for question 1 Question 2: Amplifier Configurations The signal source in the circuit below is vs = 5 sin(100000πt)mV. The transistor parameters are β = 120, and the capacitors are 10 μF (a) Design the circuit such that IC = 0.25 mA and VCE = 3 V. (b) Find the open circuit voltage gain Avo (c) Find the input resistance Rin (from the base of the transistor) (d) Find the output resistance (e) Use the amplifier model (Avo, Rin, Ro) to find vo(t). Circuit for question 2 Question 3: Amplifier Configurations Consider the circuit shown. The transistor current gain β = 180. and the source signal has a frequency of 100 kHz and the capacitors are 10 μF Note that the current source is replaced by an open circuit in the small signal model equivalent circuit. Determine: (a) the voltage gain from source to load, (b) the input resistance seen by the source (c) the output resistance
The shown circuit is called a difference amplifier, a) Assume that R1 = 15 k and R2 = 50 k, find the differential gain vO vI2−vI1 b) express the output voltage vO in terms of R1, R2, and (vI2−vI1) c) Design the difference amplifier such that the differential gain is 20 and the maximum resistor value is 500k d) What is the output vO if vI2 = vI1
Problem 4 Given: A difference amplifier shown below With a circuit parameter R1 = R3 = 5 kΩ and R2 = R4 = 200 kΩ Required: Assuming the op amp to be ideal, a) Find the voltage gain Vd/V16(10 p) b) Find the value of the differential input resistance Rid and the output resistance R0 c) If the two key resistance ratios (R2/R1) and (R4/R3) are different from each other by 2% what do you expect the common gain Acm to be? Express your answer in dB. d) Find the value of Common Mode Rejection Ratio (CMRR) of case (c). Solution:
2.63 Find the voltage gain vO/vId for the difference amplifier of Fig. 2.16 for the case R1 = R3 = 5 kΩ and R2 = R4 = 50 kΩ. What is the differential input resistance Rid? If the two key resistance ratios (R2/R1) and (R4/R3) are different from each other by 1%, what do you expect the common-mode gain Acm to be? Also, find the CMRR in this case. Neglect the effect of the ratio mismatch on the value of Ad. Figure 2.16
Using the difference amplifier configuration below, and assuming an ideal op amp; design the circuit to provide the following differential gains. In each case, the differential input resistance should be 20 kΩ. (Hint: Assume R1 = R3, R2 = R4) (a) 100 V/V (b) 0.5 V/V
Differential Amplifier: a. For the circuit below, derive an expression for the V0 in relation to V1 and V2. b. For a differential amplifier to reject common signal between the inputs V1 and V2, define a relationship between resistors R1 and R2, and separately, R3 and R4. Simplify the expression from your solution to part (a) given this relationship. c. You construct the circuit on a breadboard to measure CMRR. When V1 = V2 = 0.5 V, Vo = 1 V, and when V1 = 0 V and V2 = 0.1 V, Vo = 25 V. Calculate CMRR in dB.