Problem 1: Common-emitter amplifier
For the following, VCC = 5V, VS = 1V, RS = 1k, Ibias = 100µA, RC = 10k, CL = 10pF, = 100, VA = 100V, VT = 25mV, and IS = 10-16A.
a) Calculate the input impedance of the amplifier, Zin. Note: This does not include RS.
b) Find an expression for the transfer function, Vout/VS. Be sure to account for attenuation due to Zin.
c) Calculate the DC gain and transit frequency fT.
Problem 2: Opamp nonidealities
Assume the opamp has infinite gain and bandwidth. VOS = 1mV, and IB = −1nA. Rf = 10Ri.
a) Determine an expression for the output offset voltage, including the contributions from both VOS and IB.
b) Assuming RS = 0, calculate values for Ri and Rf that result in zero output offset.
c) Assuming RS = 1k and VOS = 0, calculate values for Ri and Rf 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 (Rin and Ro) for the opamp. Let Rf = 10Rin.
a) Determine the DC gain and the 3dB frequency of the closed loop transfer function
(Vout/Vin).
b) 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.
c) 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.
d) 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%.
