Analog Circuit Design Laboratory Report - MyWeb at WIT ...

More documents

Recommendations

Info

the op-amp is working as an inverting comparator where when Ei crosses Vref, negative to positive, VO is inverted and goes from +Vsat to –Vsat. When Ei crosses Vref, positive to negative, VO is inverted and goes from –Vsat to +Vsat. Voltage comparators can be used in many applications such as zero-crossing detectors. Another important function of the op-amp is as a voltage amplifier. There are three main circuits that define many of the amplification uses of the op-amp. They are an inverting amplifier, non-inverting amplifier, and a voltage follower. All of these circuits work off of the of the ideal circuit function of an op-amp. 2 As previously discussed, the basic circuit function of the ideal op-amp is to sense a differential voltage, Ed, between the voltage inputs signals applied to the op-amp’s two input terminals 3 . These two inputs have the characteristic of infinite resistance ideally, meaning that there is no current entering their terminals. The voltage output is the product of the differential voltage multiplied by the open loop gain, AOL, which for an ideal op-amp is considered to be infinite. These two main circuit functions of AOL and Ed combine to be known as a differential-input single-ended-output amplifier. However, the idea of an infinite gain is not practical and the op-amp will never be used alone for this reason. The op-amp is combined with additional passive components in a feedback circuit to provide a finite gain, known as the closed-loop gain, ACL. The finite gain can be manipulated to ultimately produce a variety of applicable functioning circuits, specifically the inverting amplifier, the non-inverting amplifier and the voltage follower. 2 Ibid Pg. 65 3 Ibid Pg.65 6
Negative feedback occurs when the output is returned to the negative input. It can be used to reverse the direction of change. In amplifiers when the output is fed back to the negative input, the inverted distortions cancel out the distortions produced by the amplifier itself. In an op-amp circuit negative feedback exists if a connection is between the output terminal (pin 6) and the inverting input terminal (pin 2). This connection can be may be made with anything that supports a DC current including a wire, resistor, or battery. Three basic assumptions are used when explaining the effects of negative feedback. First, the bias current for both the inverting and non-inverting inputs is equal to zero. Second, the differential voltage Ed is approximately 0V. Finally, the voltage on the non-inverting input with respect to ground is equal to the voltage on the inverting input with respect to ground. The inverting amplifier produces an output voltage, see Equation 5, which is equal to the input voltage Vin times by the closed-loop gain, ACL, given in Equation 5. The ACL is derived from Equation 5 on principals of Ohm’s Law, see Equation 6. A voltage source is connected to the op-amp’s inverting input, (pin 2) and is grounded at the non- inverting input (pin 3), see Figure 3. V out ACL ∗VDIFF . Input 1 = Eq. (5) V = I ∗ R Eq. (6) 1 7 1
Page 1 and 2: EVALUATING OPERATIONAL AMPLIFIERS I
Page 3 and 4: The ideal op-amp generally has 5 te
Page 5: ended output voltage Vo is equal th
Page 9 and 10: The non-inverting amplifier works s
Page 11 and 12: In association with the non-inverti
Page 13 and 14: Figure 7- Instrumentation Amplifier
Page 15 and 16: favorably both voltages being withi
Page 17 and 18: The next configuration, with a 10-k
Page 19 and 20: Figure 11- Positive Isc at approxim
Page 21 and 22: Figure 13- Plot of Ei versus time a
Page 23 and 24: Using the information derived from
Page 25 and 26: The output voltage can be altered s
Page 27 and 28: Analysis of an Inverting Amplifier
Page 29 and 30: 180º phase shift from the Vin. The
Page 31 and 32: The oscilloscope had the input volt
Page 33 and 34: Voltage (V) 8 6 4 2 0 -2 -4 -6 -8 F
Page 35 and 36: Voltage (V) 6 4 2 0 -2 -4 -6 Figure
Page 37 and 38: could be reduced to 1-kΩ. To decr
Page 39 and 40: The 10-kΩ potentiometer was then
Page 41 and 42: input stage VO’ was calculated to
Page 43 and 44: Adding Vref to an instrumentation a
Page 45 and 46: 1851g 4 lbs. 19.74 mV 2268g 5 lbs.
Page 47 and 48: Roff was calculated to be a 1.2-M
Page 49 and 50: Through the use of negative feedbac

Analog Circuit Design Laboratory Report - MyWeb at WIT ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?