[SOLVED] UWEE538 Midterm

Description

Problem 1: Common-emitter amplifier

For the following, V_CC = 5V, V_S = 1V, R_S = 1k, I_bias = 100µA, R_C = 10k, C_L = 10pF,  = 100, V_A = 100V, V_T = 25mV, and I_S = 10^-16A.

1. (10 points) Calculate the input impedance of the amplifier, Z_in. Note: This does not include R_S.
2. (10 points) Find an expression for the transfer function, V_out/V_S. Be sure to account for attenuation due to Z_in.
3. (10 points) Calculate the DC gain and transit frequency f_T.

Problem 2: Opamp nonidealities

Assume the opamp has infinite gain and bandwidth. V_OS = 1mV, and I_B  = −1nA. R_f = 10R_i.

1. (15 points) Determine an expression for the output offset voltage, including the contributions from both V_OS and I_B.
2. (10 points) Assuming R_S = 0, calculate values for R_i and R_f that result in zero output offset.
3. (10 points) Assuming R_S = 1k and V_OS = 0, calculate values for R_i and R_f that result in zero output offset.

Problem 3. Opamp AC and transient analysis

             Figure 3a. Non-inverting amplifier                   Figure 3b. Opamp open-loop frequency response

Figure 3. Input waveform for c) and d)

Assume ideal input/output resistances (R_in and R_o) for the opamp. Let R_f = 10R_in.

1. (10 points) Determine the DC gain and the 3dB frequency of the closed loop transfer function

(Vout/Vin).

7. (7.5 points) Provide an expression for the transient response of the amplifier for a voltage step input of 0 to 100mV. Sketch the response and label all relevant times/voltages.
8. (10 points) Assume the amplifier is driven by the input waveform shown in Fig 3c. Determine the minimum period T for which 0.1% settling is achieved during each half-period (integer multiples of T/2). Sketch the output waveform.
9. (7.5 points) Calculate the total worst-case error in the output voltage (at the end of each halfperiod) if the resistors have a tolerance of 0.1%.