ELEC 242 Lab

Experiment 4.2

The Inverting Configuration

Equipment

Components

As we saw in the previous experiment, the op-amp isn't very useful (as an amplifier) in an "open-loop" configuration (i.e. without feedback). The most common configuration for op-amp circuits is the inverting amplifier where the output is an amplified and inverted version of the input (i.e. $A$ is negative).

Part 1: The Basic Inverting Amplifier



Step 1:

 Wire the following circuit using 10 k$\Omega$ resistors for both $R_1$ and $R_F$ .
\includegraphics[scale=0.650000]{inv_opamp.ps}


Step 2:

 Set the function generator to produce a 1 V p-p, 100 Hz sine wave. Measure the voltage gain, $A_v = \frac{V_{out}}{V_{in}}$ . Since 100 Hz is within the frequency range of the DMM, you could use either the DMM or the scope to measure $V_{out}$ and $V_{in}$ However, you should always use the scope to view the waveform being measured to make sure it is what you think it is. We will see several waveforms in this lab that aren't.

In particular, note that the output is inverted with respect to the input.

Step 3:

 Replace $R_F$ with a 100 k$\Omega$ resistor. Measure the gain.

Step 4:

 Increase the input amplitude until output clipping occurs. Note the output clipping levels. Are these the same as the output levels in Exp. 4.1?