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Dialogue: 0,0:00:05.60,0:00:08.65,Default,,0000,0000,0000,,>> In this video, we'll discuss the basics of
Dialogue: 0,0:00:08.65,0:00:11.60,Default,,0000,0000,0000,,implementing operational amplifier based circuits.
Dialogue: 0,0:00:11.60,0:00:14.17,Default,,0000,0000,0000,,Main points to look for are the fact that we have to
Dialogue: 0,0:00:14.17,0:00:16.98,Default,,0000,0000,0000,,apply power to our Op-Amps to make them work,
Dialogue: 0,0:00:16.98,0:00:21.62,Default,,0000,0000,0000,,and that the output voltage from the Op-Amp is limited by the power supply voltages.
Dialogue: 0,0:00:21.62,0:00:24.10,Default,,0000,0000,0000,,These are probably two of the points that get
Dialogue: 0,0:00:24.10,0:00:27.66,Default,,0000,0000,0000,,overlooked most often when we analyze Op-Amps circuits,
Dialogue: 0,0:00:27.66,0:00:31.86,Default,,0000,0000,0000,,but they have a huge effect when we build and test a circuit.
Dialogue: 0,0:00:31.86,0:00:34.99,Default,,0000,0000,0000,,First, let's just briefly go over the rules that we
Dialogue: 0,0:00:34.99,0:00:38.23,Default,,0000,0000,0000,,use to analyze operational amplifier based circuits.
Dialogue: 0,0:00:38.23,0:00:41.29,Default,,0000,0000,0000,,The Op-Amp circuit schematic symbol is shown here.
Dialogue: 0,0:00:41.29,0:00:45.12,Default,,0000,0000,0000,,Op-Amps typically have five or more terminals.
Dialogue: 0,0:00:45.12,0:00:50.36,Default,,0000,0000,0000,,The operational amplifier has two inputs and one output terminal.
Dialogue: 0,0:00:50.36,0:00:54.86,Default,,0000,0000,0000,,The ideal operational amplifier rules are that there are no voltage difference
Dialogue: 0,0:00:54.86,0:01:00.70,Default,,0000,0000,0000,,between the input terminals and no current flowing into the input terminals.
Dialogue: 0,0:01:00.70,0:01:07.46,Default,,0000,0000,0000,,Two of the terminals V plus and V minus are used to provide power to the operational
Dialogue: 0,0:01:07.46,0:01:08.38,Default,,0000,0000,0000,,amplifier.
Dialogue: 0,0:01:08.38,0:01:12.68,Default,,0000,0000,0000,,The Op-Amp will not function if you don't apply power to these terminals.
Dialogue: 0,0:01:12.68,0:01:17.42,Default,,0000,0000,0000,,To complicate things, these terminals are sometimes not even evident on circuit diagrams.
Dialogue: 0,0:01:17.42,0:01:20.15,Default,,0000,0000,0000,,We just assume that they're there and let it go with that.
Dialogue: 0,0:01:20.15,0:01:22.55,Default,,0000,0000,0000,,When we analyze ideal Op-Amps,
Dialogue: 0,0:01:22.55,0:01:26.64,Default,,0000,0000,0000,,we generally don't assume anything about the voltage and current at the output terminal.
Dialogue: 0,0:01:26.64,0:01:31.16,Default,,0000,0000,0000,,However, there are some practical limitations associated with these parameters.
Dialogue: 0,0:01:31.16,0:01:36.29,Default,,0000,0000,0000,,The output voltage is restricted to being between the power supply voltage is
Dialogue: 0,0:01:36.29,0:01:41.87,Default,,0000,0000,0000,,V+ and V- and the output current is limited by the design of the Op-Amp itself.
Dialogue: 0,0:01:41.87,0:01:44.78,Default,,0000,0000,0000,,The Op-Amps in Digilent unlike, parts kit are provide
Dialogue: 0,0:01:44.78,0:01:49.45,Default,,0000,0000,0000,,relatively little current but higher current devices are available.
Dialogue: 0,0:01:49.45,0:01:54.44,Default,,0000,0000,0000,,Finally, one very important point relative to the voltages on this diagram,
Dialogue: 0,0:01:54.44,0:01:58.07,Default,,0000,0000,0000,,they should all be relative to the same reference voltage.
Dialogue: 0,0:01:58.07,0:02:01.76,Default,,0000,0000,0000,,This isn't a big deal if your using only the analog discovery,
Dialogue: 0,0:02:01.76,0:02:06.23,Default,,0000,0000,0000,,since all of the voltages provided by it are automatically relative to the same voltage.
Dialogue: 0,0:02:06.23,0:02:09.23,Default,,0000,0000,0000,,But if you're using other sources of power in your circuit,
Dialogue: 0,0:02:09.23,0:02:13.82,Default,,0000,0000,0000,,you may need to physically interconnect them to ensure a common reference.
Dialogue: 0,0:02:13.82,0:02:16.58,Default,,0000,0000,0000,,All the labs in this chapter specify use of
Dialogue: 0,0:02:16.58,0:02:20.30,Default,,0000,0000,0000,,the OP27 Op-Amp from the digital and analog parts kit.
Dialogue: 0,0:02:20.30,0:02:22.79,Default,,0000,0000,0000,,So, I want to spend a little time talking about
Dialogue: 0,0:02:22.79,0:02:26.27,Default,,0000,0000,0000,,the physical pin descriptions for that Operational Amplifier.
Dialogue: 0,0:02:26.27,0:02:28.85,Default,,0000,0000,0000,,The general comments I'll make for this Op-Amp will
Dialogue: 0,0:02:28.85,0:02:31.34,Default,,0000,0000,0000,,be typical for most operational amplifiers,
Dialogue: 0,0:02:31.34,0:02:35.26,Default,,0000,0000,0000,,but the specific pin descriptions may vary from Op-Amp to Op-Amp.
Dialogue: 0,0:02:35.26,0:02:38.52,Default,,0000,0000,0000,,In order to find the pin descriptions for any given Op-Amp,
Dialogue: 0,0:02:38.52,0:02:40.65,Default,,0000,0000,0000,,simply look up a datasheet online.
Dialogue: 0,0:02:40.65,0:02:43.73,Default,,0000,0000,0000,,One of the first pieces of information on the sheet will generally be
Dialogue: 0,0:02:43.73,0:02:47.87,Default,,0000,0000,0000,,a picture similar to this one with a description of the pin functions.
Dialogue: 0,0:02:47.87,0:02:52.60,Default,,0000,0000,0000,,First, a couple of comments about Operational Amplifiers in general.
Dialogue: 0,0:02:52.60,0:02:56.96,Default,,0000,0000,0000,,Op-Amps which can be used in a solderless breadboard are generally in what are
Dialogue: 0,0:02:56.96,0:03:00.56,Default,,0000,0000,0000,,called dual in-line packages abbreviated as DIP.
Dialogue: 0,0:03:00.56,0:03:05.56,Default,,0000,0000,0000,,This simply means that the pins are oriented in two rows of pairs.
Dialogue: 0,0:03:05.56,0:03:08.81,Default,,0000,0000,0000,,The spacing of the pins allows the chip to be inserted in
Dialogue: 0,0:03:08.81,0:03:13.52,Default,,0000,0000,0000,,a solderless breadboard with the central channel of the breadboard separating the rows.
Dialogue: 0,0:03:13.52,0:03:18.14,Default,,0000,0000,0000,,This ensures that any pin is electrically isolated from any other pin.
Dialogue: 0,0:03:18.14,0:03:23.72,Default,,0000,0000,0000,,Second, the orientation of the pins is specified by a notch at one end of the chip,
Dialogue: 0,0:03:23.72,0:03:25.90,Default,,0000,0000,0000,,or a dot in one corner of the chip.
Dialogue: 0,0:03:25.90,0:03:28.10,Default,,0000,0000,0000,,Many chips have both of these indicators.
Dialogue: 0,0:03:28.10,0:03:31.31,Default,,0000,0000,0000,,If you're looking down at the chips with the notches at the top,
Dialogue: 0,0:03:31.31,0:03:34.78,Default,,0000,0000,0000,,pin one will be in the upper left-hand corner of the chip.
Dialogue: 0,0:03:34.78,0:03:39.70,Default,,0000,0000,0000,,Other pins are numbered successively in a counterclockwise direction.
Dialogue: 0,0:03:39.70,0:03:43.43,Default,,0000,0000,0000,,Alternately, if you use the dot to orient the pins,
Dialogue: 0,0:03:43.43,0:03:45.70,Default,,0000,0000,0000,,the dot is closest to pin one.
Dialogue: 0,0:03:45.70,0:03:49.40,Default,,0000,0000,0000,,Now, let's take a look at some physical Op-Amps themselves.
Dialogue: 0,0:03:49.40,0:03:52.05,Default,,0000,0000,0000,,This is the OP27 Op-Amp.
Dialogue: 0,0:03:52.05,0:03:55.70,Default,,0000,0000,0000,,The Op-Amp type is printed directly on the top of the chip.
Dialogue: 0,0:03:55.70,0:03:59.52,Default,,0000,0000,0000,,It has eight pins in two rows of four each.
Dialogue: 0,0:03:59.52,0:04:02.12,Default,,0000,0000,0000,,It's been inserted into the breadboard correctly with
Dialogue: 0,0:04:02.12,0:04:06.04,Default,,0000,0000,0000,,the central channel of the breadboard between the two rows of pins.
Dialogue: 0,0:04:06.04,0:04:11.22,Default,,0000,0000,0000,,This particular Op-Amp has both a notch and a dot to indicate pin one.
Dialogue: 0,0:04:11.22,0:04:13.52,Default,,0000,0000,0000,,The other pins are numbered counterclockwise,
Dialogue: 0,0:04:13.52,0:04:15.04,Default,,0000,0000,0000,,so this is pin two,
Dialogue: 0,0:04:15.04,0:04:18.38,Default,,0000,0000,0000,,three, four, five and so on.
Dialogue: 0,0:04:18.38,0:04:23.24,Default,,0000,0000,0000,,>> The individual pin descriptions for the OP27 Op-Amp are shown here.
Dialogue: 0,0:04:23.24,0:04:27.90,Default,,0000,0000,0000,,Pins two and three are the inverting and non-inverting inputs.
Dialogue: 0,0:04:27.90,0:04:30.60,Default,,0000,0000,0000,,Pin six is the output terminal.
Dialogue: 0,0:04:30.60,0:04:33.50,Default,,0000,0000,0000,,The positive voltage supply is connected to pin
Dialogue: 0,0:04:33.50,0:04:37.38,Default,,0000,0000,0000,,seven and the negative voltage supply is connected to pin four.
Dialogue: 0,0:04:37.38,0:04:42.38,Default,,0000,0000,0000,,Pins one and eight are offset voltage trim terminals.
Dialogue: 0,0:04:42.38,0:04:45.06,Default,,0000,0000,0000,,These can be used to fine tune the Op-Amp behavior,
Dialogue: 0,0:04:45.06,0:04:47.08,Default,,0000,0000,0000,,but we won't use them in this course.
Dialogue: 0,0:04:47.08,0:04:49.70,Default,,0000,0000,0000,,Pin five doesn't do anything.
Dialogue: 0,0:04:49.70,0:04:53.26,Default,,0000,0000,0000,,It's said to be not connected or NC.
Dialogue: 0,0:04:53.26,0:04:56.35,Default,,0000,0000,0000,,We will always need to provide power to our circuit.
Dialogue: 0,0:04:56.35,0:04:58.24,Default,,0000,0000,0000,,So, I'll go ahead and connect the voltage supplies
Dialogue: 0,0:04:58.24,0:05:00.68,Default,,0000,0000,0000,,now before we wire up our example circuit.
Dialogue: 0,0:05:00.68,0:05:03.68,Default,,0000,0000,0000,,This pin is the positive voltage supply,
Dialogue: 0,0:05:03.68,0:05:06.30,Default,,0000,0000,0000,,this pin is the negative voltage supply.
Dialogue: 0,0:05:06.30,0:05:09.27,Default,,0000,0000,0000,,I'll use V plus on my analog discovery for
Dialogue: 0,0:05:09.27,0:05:14.24,Default,,0000,0000,0000,,the positive voltage supply and V minus for the negative voltage supply.
Dialogue: 0,0:05:14.24,0:05:18.28,Default,,0000,0000,0000,,I generally connect my power supplies first. Since my experience has been that
Dialogue: 0,0:05:18.28,0:05:23.03,Default,,0000,0000,0000,,forgetting to connect these as my number one silly mistake when wiring circuits.
Dialogue: 0,0:05:23.03,0:05:24.82,Default,,0000,0000,0000,,For this video, we'll create
Dialogue: 0,0:05:24.82,0:05:28.84,Default,,0000,0000,0000,,this inverting voltage amplifier circuit and investigate it's response.
Dialogue: 0,0:05:28.84,0:05:30.24,Default,,0000,0000,0000,,If we analyze this circuit,
Dialogue: 0,0:05:30.24,0:05:31.77,Default,,0000,0000,0000,,we'll find that the output voltage,
Dialogue: 0,0:05:31.77,0:05:36.50,Default,,0000,0000,0000,,V-out, should be negative two times the input voltage, V-in.
Dialogue: 0,0:05:36.50,0:05:41.02,Default,,0000,0000,0000,,We've already connected V plus and V minus to the positive and negative voltage supplies.
Dialogue: 0,0:05:41.02,0:05:47.14,Default,,0000,0000,0000,,So, all that remains is to add the resistors in the circuit and apply an input voltage.
Dialogue: 0,0:05:47.14,0:05:49.09,Default,,0000,0000,0000,,We'll use channel one of
Dialogue: 0,0:05:49.09,0:05:52.99,Default,,0000,0000,0000,,our waveform generator to apply the input voltage to this circuit.
Dialogue: 0,0:05:52.99,0:05:55.16,Default,,0000,0000,0000,,According to our circuit schematic,
Dialogue: 0,0:05:55.16,0:06:00.68,Default,,0000,0000,0000,,we have a 20 kilo ohm resistor connecting the output terminal to the inverting input,
Dialogue: 0,0:06:00.68,0:06:03.51,Default,,0000,0000,0000,,a 10 kilo ohm resistor connecting
Dialogue: 0,0:06:03.51,0:06:07.94,Default,,0000,0000,0000,,our inverting input to the arbitrary waveform generators channel one,
Dialogue: 0,0:06:07.94,0:06:10.45,Default,,0000,0000,0000,,which is this yellow wire,
Dialogue: 0,0:06:12.00,0:06:18.14,Default,,0000,0000,0000,,and we need to ground the non-inverting input terminal.
Dialogue: 0,0:06:18.14,0:06:22.28,Default,,0000,0000,0000,,We'll use channel one of our voltmeter to measure our output voltage.
Dialogue: 0,0:06:22.28,0:06:26.63,Default,,0000,0000,0000,,We'll measure that between this terminal and ground.
Dialogue: 0,0:06:27.56,0:06:29.70,Default,,0000,0000,0000,,To demonstrate our circuit,
Dialogue: 0,0:06:29.70,0:06:32.55,Default,,0000,0000,0000,,first we'll have to apply power to the power supplies.
Dialogue: 0,0:06:32.55,0:06:35.84,Default,,0000,0000,0000,,I'm going to turn on the voltage instrument.
Dialogue: 0,0:06:35.84,0:06:40.80,Default,,0000,0000,0000,,Now, let's start by applying a relatively small voltage to the input,
Dialogue: 0,0:06:40.80,0:06:42.56,Default,,0000,0000,0000,,say half a volt.
Dialogue: 0,0:06:42.56,0:06:45.04,Default,,0000,0000,0000,,Turning on the waveform generator,
Dialogue: 0,0:06:45.04,0:06:50.16,Default,,0000,0000,0000,,we see that our output is about negative one volts which is exactly what we would expect.
Dialogue: 0,0:06:50.16,0:06:52.51,Default,,0000,0000,0000,,Increasing this to one volt,
Dialogue: 0,0:06:52.51,0:06:55.08,Default,,0000,0000,0000,,the output is about negative two volts.
Dialogue: 0,0:06:55.08,0:06:57.61,Default,,0000,0000,0000,,It's negative two times the input.
Dialogue: 0,0:06:57.61,0:06:59.86,Default,,0000,0000,0000,,To emphasize the inversion property,
Dialogue: 0,0:06:59.86,0:07:01.54,Default,,0000,0000,0000,,if I input negative one volt,
Dialogue: 0,0:07:01.54,0:07:04.09,Default,,0000,0000,0000,,I should get positive two volts out.
Dialogue: 0,0:07:04.09,0:07:07.40,Default,,0000,0000,0000,,Now, let's take a look at the saturation of the amplifier.
Dialogue: 0,0:07:07.40,0:07:09.50,Default,,0000,0000,0000,,If we go up to two volts,
Dialogue: 0,0:07:09.50,0:07:13.34,Default,,0000,0000,0000,,we get about negative four volts out which is what we would expect.
Dialogue: 0,0:07:13.34,0:07:16.56,Default,,0000,0000,0000,,Increasing this to three volts, however,
Dialogue: 0,0:07:16.56,0:07:21.91,Default,,0000,0000,0000,,just brings the output up to a little bit over four volts. We've saturated.
Dialogue: 0,0:07:21.91,0:07:25.21,Default,,0000,0000,0000,,We've gotten as close to the voltage supplies as we can.
Dialogue: 0,0:07:25.21,0:07:30.98,Default,,0000,0000,0000,,Increasing the input even more will not change our output.
Dialogue: 0,0:07:34.38,0:07:37.52,Default,,0000,0000,0000,,That's really all there is to Op-Amps for now.
Dialogue: 0,0:07:37.52,0:07:39.74,Default,,0000,0000,0000,,All of the lab assignments in this chapter you use
Dialogue: 0,0:07:39.74,0:07:43.06,Default,,0000,0000,0000,,these basic tools, but apply them to different Op-Amp circuits.
Dialogue: 0,0:07:43.06,0:07:45.81,Default,,0000,0000,0000,,Makes sure that you apply voltage to your Op-Amps for
Dialogue: 0,0:07:45.81,0:07:48.80,Default,,0000,0000,0000,,all your circuits and the lab should be pretty straightforward.
Dialogue: 0,0:07:48.80,0:07:52.20,Default,,0000,0000,0000,,The only thing to look for is that the ideal Op-Amp behavior breaks
Dialogue: 0,0:07:52.20,0:07:56.78,Default,,0000,0000,0000,,down if the output gets too close to the supply voltage rails.