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Unformatted text preview: MAE180 Laboratory Project 2 Basic operational amplifier circuits EXPERIMENT #1: open loop test circuit. DESCRIPTION The physical package of an op-amp has more terminals than the 3-terminal symbol used in class to represent it. The figures below show the 8 pin, dual in line package (DIP) for the common LF411 op-amp, together with a typical connection diagram (inverting amplifier with a 10k potentiometer for correcting/trimming the input offset voltage) In this first op-amp lab we will ignore terminals 1 and 5 (used to eliminate offset voltages); terminal 8 is not used by this op-amp. The goals of this experiment are to make the basic connections of an op-amp, and demonstrate its very large open loop gain. LABORATORY EQUIPMENT Oscilloscope. Electronic teaching station. LabJack. Jumpers, 2 BNC cable, 2 alligator clip to BNC connector, One LF411 op-amp, two 8 pin DIP socket, one 1M resistors. LABORATORY PROCEDURE 1. Do not touch the op-amp. You will need to be grounded by a wrist band before picking up the op-amp (see 6]).Use the waveform generator to create a sinusoidal signal with amplitude of 1 V, zero offset and a frequency of 1 Hz. You will use this signal as the input signal shown in the sketch. Use the oscilloscope to find the settings of the waveform generator. 2. Turn off the station. 3. Build the circuit on the prototype board. DO NOT INSERT THE OP-AMP YET. Insert the 8 pin socket instead (note that both the socket and the op-amp have indentations indicating the position of terminal 1). DO NOT CONNECT THE INPUT SIGNAL YET (see 8] below). Use the 12V DC voltage supply provided by the station (constant DC voltage outputs below the GND terminal) to power terminals 4 and 7 of the socket. You will need the 1M resistor to create a path to ground for the very small, but finite, input offset current of the non inverting input. 4. Use a voltmeter to make sure that voltages of terminals 4 and 7 are -12V and +12V respectively. Your voltage reference, or circuit ground, is the terminal GND of the station. 5. Turn off the station. 6. Ground yourself using a wrist band. Pick up the op-amp and insert it in the socket. You may have to bend the terminals of the op-amp to be able to insert it. Be gentle with the op-amp terminals, they easily break off. Make sure to insert the op-amp in the correct terminals of the socket. 7. Turn on the station. Measure the output voltage. It should be saturated. Do not touch the op-amps terminals directly, use a jumper inserted in a nearby station orifice....
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- Spring '09