F2023-3EJ4_Lab04

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Jan 9, 2024

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Page 1 McMaster University Electrical and Computer Engineering Department EE3EJ4 Electronic Devices and Circuits II - Fall 2023 Lab. 4 Feedback Circuits Lab Report Due on Nov. 19, 2023 Objective: To design and characterize a negative feedback amplifier and an oscillator. Attributes Evaluated: These are the attributes you need to demonstrate in your solutions.  Competence in specialized engineering knowledge to simulate circuit performance using a SPICE-based circuit simulator and conduct analog circuit debugging;  Ability to obtain substantiated conclusions as a result of a problem solution, including recognizing the limitations of the approaches and solutions and  Ability to assess the accuracy and precision of results. Test Equipment:  Analog Discovery 2 (AD2)  WaveForms from Digilent Link and WaveForms Reference Manual  Analog Discovery 2 Quick Start Series Videos Components:  Op-Amp: 1  TLV2371  Transistors: 6  NPN-BJT 2N3904 3  PNP-BJT 2N3906  Resistors: 3  8.06 k Ω resistor 3  76.8 k Ω resistor 3  57.6 k Ω resistor 2  8.06 k Ω resistor 2  8.25 k Ω resistor 2  100 k Ω resistor 1  240 k Ω resistor  Capacitors: 2  1 nF (102) capacitor Information of Components: For a detailed description of these transistors, please check the following websites: https://www.onsemi.com/products/discretes-drivers/general-purpose-and-low-vcesat-transistors/2n3904 or https://www.onsemi.com/pub/Collateral/2N3903-D.PDF https://www.onsemi.com/products/discretes-drivers/general-purpose-and-low-vcesat-transistors/2n3906 or https://www.onsemi.com/pub/Collateral/2N3906-D.PDF For the description of Op-Amp TLV2371 and its SPICE model, please check the following websites: https://www.ti.com/product/TLV2371?dcmp=dsproject&hqs=sw&#design-development##design- tools-simulation Reminder: Switch off the DC power suppliers first whenever you need to change the circuit configurations. Turn on the DC power only when you no longer change the circuit connection.

Page 2 Part 1: Negative Feedback Amplifier Description of the Negative Feedback Amplifier In this lab, we design a negative feedback amplifier using a directly coupled (DC), multi-stage operational (Op) amplifier (Amp). We then construct a feedback amplifier by connecting the output of the Op-Amp. In this section, we first characterize the Op-Amp and then characterize the voltage gain and frequency response of the negative feedback amplifier using the feedback theory. A. SPICE Simulation – Op-Amp Characterization 1.1 In PSpice , construct the Op-Amp, as shown in Fig. 1, using the common-emitter (CE) amplifier from Lab 2, the common-collector (CC) amplifier, and the differential amplifier with a current mirror load from Lab 3. Here, I x is a current test source used to characterize the output resistance of the Op-Amp. 1.2 Voltage Gain: Set the DC values of V 1 and V 2 = 0 V and their AC amplitude 1 mV. Set the DC and AC values of the test current source I x to zero. For the differential mode signal, set the phases of the AC signal V 1 and V 2 to be 0  and 180  , respectively, as shown in Fig. 1. In this setting, the differential-model signal v id = V 1 – V 2 = 1 mV – (–1 mV) = 2 mV. Conduct AC analysis to obtain the base current i b 1 of Q1, the voltages V o 1 , V o 2 , and V o at the base of Q8, the base of Q9, and the emitter of Q9, respectively. Set the AC sweep type in Logarithmic with Start Frequency = 100 Hz, End Frequency = 100 kHz, and Points/Decade = 101. Record the simulated magnitude and phase of i b 1 , V o 1 , V o 2 , and V o in the sheet “Step 1.2” of the Excel file “Lab 4 – Feedback Circuit.xlsx”. Fig. 1 Schematic diagram of the directly coupled (DC), multi-stage operational amplifier

Page 3 1.3 Frequency Response: Set the DC and AC values of V 1 and V 2 = 0 V. Set the DC value of I x = 0 A and AC amplitude of the test current source I x to 1 mA. Since SPICE uses a passive sign convention, i.e., positive current flows from the (+) node of the current source to its (-) node, we set its AC phase of I x to 180  for the current flowing into V o , as required by the linear two-port network theory. Conduct AC analysis to obtain V o at the emitter of Q9. Set the AC sweep type in Logarithmic with Start Frequency = 100 Hz, End Frequency = 100 kHz, and Points/Decade = 101. Record the simulated magnitude and phase of V o in the sheet “Step 1.3” of the Excel file “Lab 4 – Feedback Circuit.xlsx”. B. SPICE Simulation – Negative Feedback Amplifier 1.4 Construct the negative feedback amplifier in PSpice using the circuit diagram shown in Fig. 2, with resistance values and supply voltages specified in the figure. 1.5 To place the sinusoidal voltage source V1, access the Modeling Application with Place -> PSpice Part -> Modeling Application, and select Sources -> Independent Sources. In the dialogue box, choose Sine -> Voltage -> Sine, and set the Offset value VOFF = 0 V, VAMPL = 1 mV, Frequency = 1 kHz, Phase = 0  , DC = 0 V, and AC = 1 mV, respectively. 1.6 Voltage Gain: Conduct Transient Response simulation for V o at the emitter of Q9 with Run to Time TSTOP = 6 mS and Maximum Step Size = 25us. Record the output voltage V o versus time in the sheet “Step 1.6” of the Excel file “Lab 4 – Feedback Circuit.xlsx”. Fig. 2 Schematic diagram of the negative feedback amplifier

Page 4 1.7 Frequency Response: Conduct an AC analysis to obtain V o at the emitter of Q9. Set the AC sweep type in Logarithmic with Start Frequency = 1 kHz, End Frequency = 10 MegHz, and Points/Decade = 101. Record the simulated magnitude and phase of V o in the sheet “Step 1.7” of the Excel file “Lab 4 – Feedback Circuit.xlsx”. C. AD2 Measurement Because operational amplifiers (Op-Amps) are directly coupled devices with significant differential gains, they are prone to DC problems (e.g., mismatch), resulting in the DC offset voltage. Suppose the two input terminals of an Op-Amp are tied together and connected to the ground; even though V id = 0, a finite DC voltage still exists at the output. The output will be at the positive or negative saturation level if the Op-Amp has a high differential-mode gain. The Op-Amp output can be brought back to its ideal value of 0 V by connecting a DC offset voltage with appropriate polarity and magnitude between the two input terminals of the Op-Amp. In this lab, we first characterize this DC offset voltage of the designed Op-Amp and then use it to design a feedback amplifier. 1.8 Use the port definition diagram of the AD2 shown in Fig. 3 when setting up your circuits. 1.9 Based on Fig. 1, construct the measurement setup for an operational amplifier using the common- emitter (CE) amplifier from Lab 2 and the common-collector (CC) and differential amplifiers from Lab 3. 1.10 Use V+ = 5V for V CC and V- = -5V for V EE . Connect Scope Ch. 1 Negative (1-), Scope Ch. 2 Negative (2-), GNDV+, GNDV-, GNDW1, and GNDW2 to a common ground line.

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