The objective of this lab was to experiment with a negative feedback amplifier and predict its gain without the feedback.

Authors Avatar

20ECES465

Electronics Laboratory

Section 001

11/04/03

Objective

The objective of this lab was to experiment with a negative feedback amplifier and predict its gain without the feedback.  

Procedure

        After connecting the circuit per specifications in part one of the lab manual and verifying 7the voltage input and output we manipulated RFEEDBACK2 in order to achieve a gain of 100 v/v at a frequency of 1 KHz.  We then made a screen dump of the Acircuit value.  Since we were experimenting in the real world we could not use the ideal values for the components.  Table 1 shows the ideal values called for in the lab report and the actual resistance values measured by a multimeter.

Table 1: Resistance values


We then swept the voltage in order to find the fH frequency.  We then solved Equation 1 to get the feedback factor H.  After we isolated H we could then predict what the gain of the circuit would be without the feedback factor.

We then opened the circuit, which resulted in the RFEEDBACK2 value of infinity.  The resulting circuit gave us an output of 15.09 V with an input of .01 V.  This gave us a gain of 1509 V/V.  We then swept the frequency to determine fH without the feedback.    Then we calculated the gain-bandwidth product with and without feedback.

Join now!

Calculations/Figures

Feedback Ratio for Voltage Series Configuration

Gain Desensitization

 

Bandwidth Extension

Results

The results of the experiment in step 1 and step 2 are below in Table 2 and Table 3 respectively.  The gain of the negative feedback circuit was designed to be 100 V/V.  The high frequency 3db point was 940Khz.  When feedback was removed from the circuit the gain increased to 1509 V/V and the high frequency 3db point decreased to 185 KHz.  The applications of this are discussed in the individual discussion section.

Table 2: Feedback circuit values (step 1)

...

This is a preview of the whole essay