Download Circuit Design:

Pre-Lab Exercises
Intro-Lab
Circuit Design:
You should have read the lab handout before beginning the Pre-lab exercises, specifically
the Appendix section on the operational amplifier.
Differential Amplifier:
Figure 1 shows a 3op-amp differential amplifier design using the LM741 chip. Derive the
characteristic equation given below. This will give you experience with simple linear
circuits. All you need is the equations of an op-amp and Ohm’s Law, and the Appendix
of the Intro Lab should help as well as your book.
Figure 1: Instrumentation Amplifier using 3 LM741 OP-AMPs
Characteristic Equation:
Vo = (V2-V1) (R3/R2)(1+ (2R1/R))
Now, consider the monolithic Differential Amplifier Chip AD620. You should download
its data sheet from:
http://www.analog.com/productSelection/pdf/AD620_e.pdf
Design the amplifier for a gain of 50. See the data sheet and consult your circuit kit item
sheet, available from the course website, for a list of available resistors and use these to
for the specifics of the circuit design.
The pinout diagram for the AD620 is given in the data sheet. It is a 1 op-amp design to
function the same as the three op-amp design above. It uses one resistance Rg to
determine the gain. Pin 5 is the circuit ground and +/- Vs is the power supply voltage and
should be set to +/-12 Volts respectively.
1. Draw the circuit, its wiring diagram and write its output function.
2. Sketch the output if the input is a sine wave from -1 to 1 V and T=10 ms.
Low Pass Filter:
Consider the op-amp chip LM741 and download the data sheet from:
http://www.national.com/ds/LM/LM741.pdf
Use the data sheet and the Appendix from the Intro Lab to design a lowpass filter with a
cutoff frequency of 1 kHz. There should be an inventory list of your capacitor kit
available from the course website.
3. Draw the circuit, its wiring diagram and write its output function.
4. Write the differential equation for your modified circuit and solve it.