The data sheet said that it is single supply so I can only supply positive voltage. But I was wondering if I could put -9V on the GND and 9V on the Vdd to make the TLC272 work as a dual supply op amp?
The reason I am asking is that I was trying to create a simple inverting op amp using the TLC272, but the output is pretty much hovering a little above 0V when I was supplying a square wave from the Arduino's digital pins. This makes sense since I did not supply a negative voltage to the op amp. When I tried out the non inverting configuration, I got the expected result. So I was wondering if there is a way I can turn this op amp into a dual supply?
A total supply range of +/-9 volts is at the absolute maximum ratings of 18 volts for the device and the specified range is 16 volts. That’s just plain risky, asking for trouble. +/-5 or 6 volts is a far better choice.
I don’t see anything so special about the device, in fact it’s a thirty plus year old design. My point is there are far better, more modern choices with rail to rail inputs and outputs that operate much closer to zero volts with a single supply.
Choose wisely, don’t box yourself into creating avoidable significant issues like device failure.
I'm not sure what you are trying to achieve.
You have a single supply op amp running from the same supply as the arduino, configured as an inverting amplifier - you havent told us the gain.
Lets say its a gain of -1 (unity gain inverting)
If its a 5V unit the input (digital output) is at either +5v or +0.x V. (just a little above zero)
the amplifier output will be -5V or -0.x V
since the op amp has no negative supply it cant do that.
If you REALLY want a square wave between -5 and -0 you need a negative rail
you can easily generate that as shown on my site here
If you just want an anti-phase square wave or to buffer the output you can simply connect the non-inverting input of the op amp to your positive voltage rail.
Tell us more about what you are trying to do please - with a diagram?
tackymime:
The data sheet said that it is single supply so I can only supply positive voltage.
It says no such thing!
"Single-Supply Operation" is a feature option, not a requirement. It is an implicit consequence of two other specifications, "Output Voltage Range Includes Negative Rail" and "Common-Mode Input Voltage Range Extends Below the Negative Rail". In order for an op-amp to operate from a single supply voltage, it must operate correctly with input voltages down to the negative or "ground" rail, and must be able to pull the output completely down to ground.
This op-amp can do both of these things and so it can be used with the negative rail as ground. This is because it is a CMOS device, like almost all of the logic with which we are now familiar. Earlier op-amps could not pull the output to either supply rail and often could not handle input voltages approaching one or both supply rails, so could not be used with a zero volt supply rail.
This also means that those earlier devices required a supply voltage range significantly greater that the signal voltage - by a few volts. If like the TLC272, it will operate over almost the whole of the supply range, you only need to use supply voltages corresponding to the signal range. In this case, ±8 V or 16 V to ground if that is what you require. The 18 V absolute maximum voltage matches the 4000 series CMOS logic of the same period.
Thanks for the responses, so it is possible to use the tlc272 with negative and positive rails.
I just have a follow up question regarding how I can supply the negative and positive voltages to the tlc272 using batteries (say something like CR2 batteries)?
A battery has a + and - terminal, so if I hook up the Vdd to - and GND to +, I can provide the op amp with a negative voltage.
I imagine for creating both a positive and a negative rail I would need two batteries but I can't figure out how I can use both batteries to supply the tlc272. Is this even possible with this op amp?
Your problem can be partially solved by using the op amp in single supply configuration, but biasing the (+) input to 1/2 of the supply voltage, using a resistive voltage divider. The bias circuit is found in most op amp data sheets or application notes.
I say partially, because the outputs usually can't swing fully rail to rail. If the non-inverting gain is less than one, you should be able to get a clean square wave out.
This is just a learning experience. I am not building anything specific to a project.
I just want to use the tlc272 as an inverting op amp powered with a positive and negative rail from household batteries since I don't have some bench-top power supply.
I am planning on sending it a square wave using the arduino's digital pins to the op amp and then seeing what the output looks like.
OK. Common batteries are the 9V block cells - you cant use those because the TLC272 is not recommended for use over 16V. So your best bet is 2 sets of 4 "1.5V" batteries.
4*1.5 = 5 - 6V depending on the type.
To make it more interesting add a pot between the arduino output and inverting amplifier.
You can also try different values for R1 & R2 to change the gain.
In my diagram the logic gate output represents the arduino's output pin.
You do need to have a common ground as shown but DONT connect the battery V+ or V- to the arduino, just to the op amp.
That would produce a negative output right? The arduino wouldn't be able to read the output of the op amp. So I guess I will just include another inverting op amp after it and feed it back to the arduino.
Earlier op-amps could not pull the output to either supply rail and often could not handle input voltages approaching one or both supply rails, so could not be used with a zero volt supply rail.
