Part$-$B: The Inverting Voltage Amplifier

Background Information:

The inverting voltage amplifier is based on parallel$-$parallel negative feedback. This amplifier exhibits modest input impedance, low output impedance, and stable inverting voltage gain. The voltage gain is set by the two feedback resistors, Ri and Rf$.$

Experimental Procedure:

The voltage gain of the inverting amplifier can be determined accurately from the feedback resistors $R_i$ and $R{f}_f$ Calculate the voltage gains for the amplifier of Fig. $3$ for the Revalues specified and record them in Table $4.$

Assemble the circuit of Fig. $3$ using the $4k7$ resistor.

Set the generator to a $1$ kHz sine wave, $100$ millivolts peak.

Apply the generator to the amplifier. Measure and record the output voltage in Table $4,$ noting its phase relative to the input. Also, compute the resulting experimental voltage gain and gain deviation.

Repeat step $4$ for the remaining Rfvalues in Table $4.$

For any given $R_i,R_f$ combination, the voltage gain should be stable regardless of the precise op amp used, even if it is of an entirely different model. To verify this, first set $R{e}_f$ to $22k.$

Set the generator to a $1$ kHz sine wave, $100$ millivolts peak.

Apply the generator to the amplifier. Measure and record the output voltage in Table $5.$ Also, compute the resulting experimental voltage gain and gain deviation.

Repeat step $8$ for two other op amps.

The concept of virtual ground is very important. A virtual ground exists at the inverting input of the op amp in this circuit. Ideally, the voltage at this point should be very close to $0.$ Through voltage divider effect, this implies that all of the input signals must be dropping across $R_i,$ and thus $R{i}_i$ must establish the input impedance of the amplifier.

Set Re to $4k7.$

Set the generator to a $200$ Hz sine wave, $1$ volt peak.

Apply the generator to the amplifier. Use a DMM to measure and record the AC potential at the inverting terminal of the op amp. Record the value in Table $6.$

Data Tables

Table $4$

$\backslash$table$[[R_f,$Theoritical Av$,$Vout,Phase,Experimental Av$,\%$ Deviation$],[4k7,,,,,],[10k,,,,,],[22k,,,,,],[33k,,,,,],[47k,,,,,]]$

$\backslash$table$[[$Opamp$,$Theoritical Av$,$Vout,Experimental Av$,\%$ Deviation$],[1,,,,],[2,,,,],[3,,,,]]$

Table $6$

$\backslash$table$[[V_{\text{i}\text{n}\text{v}\text{e}\text{r}\text{t}\text{i}\text{n}-\text{i}\text{n}\text{p}\text{u}\text{t}},]]$ Opamp modle $071.\mathrm{.}072.\mathrm{.}074$