EIE3100 Lab 3 - Negative Feedback (NFB) Amplifier - 2023 S1

 

EIE3100 Lab PCB: 

(Circuit design by Mr. Nick Wong and Ir. Patrick Yip in Oct 2023)

The circuit board schematics:

Download schematics PDF file

Download Schematics (Color) + PCB File

PCB File: (Top View)

PCB Bottom View (Back side):

Download BOM of the Test Board

Potentiometer (Variable resistor) circuit:

So, please use either Pin #1 and Pin # 2, OR  Pin #2 and #3

NOT use pin # 1 and #3 (if using #1 and #3, it becomes a fixed-resistance resistor!!!)

1) Response of Basic amplifier

a) Calibrate / check your oscilloscope with its internal signal generator (2.5V peak-to-peak, 1kHz)

b) Check your signal generator with the above oscilloscope

c) Start experiment:

  i) Connect the power supply: TP9_Vcc = +12V and the negative output (-) to the ground "GND".

Connect the signal generator output to the pin "TP1_IN1" of the lab test board. Adjust the amplitude so that the amplifier output Vo is approximately 2 V RMS at 1 kHz. E.g. Amplitude at about 7 mV(rms).

Volt gain = e.g. 2.138 Vrms / 7.9 Vrms

2) Response of amplifier with NFB

Connect the poin X to Gnd (0V line).

Find the input resistance "Rin":

by measuring the voltage at TP1_IN1 and TP4_F

Cut-off Frequencies

Source: https://www.electronics-tutorials.ws/amplifier/frequency-response.html

Example Results (for reference only)

Note: This result was measured with the old NFB test board, so it should have some differences.