What's so special about getting an output of 5 V? If you've designed it properly, then any pair of (reasonable) input voltages in which v2 is 1 V greater than V1 should give you an output of 5 V.How would i design a circuit with one op amp, 2 input voltages (v1 and v2) and a power supply of +-12V to obtain an output Vo = 10(v2-v1)-5? I attempted a differential amplifier, but I don't understand how to get an output of 5??
I believe the problem is to provide an output offset of -5v, which is not necessarily trivial with only one op amp in a differential configuration.What's so special about getting an output of 5 V
I agree with above.I believe the problem is to provide an output offset of -5v, which is not necessarily trivial with only one op amp in a differential configuration.
I agree that this is probably what the TS meant -- but the TS needs to learn to communicate what they want instead of being sloppy and expecting others to read their mind.I believe the problem is to provide an output offset of -5v, which is not necessarily trivial with only one op amp in a differential configuration.
Reading between the lines, the TS probably doesn't need to worry about accuracy or need a reference because they are still at a stage where everything is ideal, including the supply rails (i.e., they can use the power supply for their reference voltage).LATER:
Yes i found a version that looks like it works but it requires a voltage reference and a couple resistors and may only be applicable to certain circuits with one input source that can stand some offset current. So no second op amp but does require a good voltage reference diode or depending on accuracy, a low voltage zener. So there would be some limitations.
Hi there,Reading between the lines, the TS probably doesn't need to worry about accuracy or need a reference because they are still at a stage where everything is ideal, including the supply rails (i.e., they can use the power supply for their reference voltage).
What is this "in the usual way" that you refer to?Hi there,
Well for this circuit, it's a differential amplifier right?
That would mean that he cant use one of the power rails for a reference for the offset in the usual way, unless he adds another op amp, and using the reference diode would be an idea to help eliminate the need for another op amp. The difference is the reference diode can be used as a floating reference voltage (given proper biasing is satisfied).
I havent looked at every possible way though, there may be another way too where we can use the power rail. Maybe you can come up with a circuit.
Sorry, but I don't think it's as "trivial" as you think....................
The circuit that deals with this is a trivial combination of a difference circuit and a summing circuit. Five resistors and one op amp.
Hello again,What is this "in the usual way" that you refer to?
The circuit that deals with this is a trivial combination of a difference circuit and a summing circuit. Five resistors and one op amp.
It's too early to show a solution. The OP isn't even 48 hours old yet -- the assignment may not be due and the TS may well be back. Let's give them a chance to show some work. I laid out an approach that is simple and doesn't even involve solving simultaneous equations, though that shouldn't be a huge factor even if it did.Hello again,
Well i think that only works if we have a negative supply rail available to act as an actual negative offset, after all this seems to require a negative output offset. So the question becomes is there a negative rail available?
I had originally assumed that the only power rails available where the +Vcc and ground. Rereading the first post though i see that he stated that he has plus and minus 12v available so that answers that. If the -12v line is STABLE then it could work, but if it is not stable then it wont work very well.
You could always show your circuit too if you like
You suggested it's a trivial combination of 5 resistors and an op amp, but is that different from the circuit in Post #12?...........
I laid out an approach that is simple and doesn't even involve solving simultaneous equations,
...............
Yes.You suggested it's a trivial combination of 5 resistors and an op amp, but is that different from the circuit in Post #12?
Hi,Yes.
Consider a traditional (inverting) summing amplifier:
View attachment 114596
Now consider a traditional one op-amp differential amplifier:
View attachment 114597
If you understand HOW a summing amplifier works, what is SO difficult about seeing how to add a fifth resistor to the diff amp such that it is taking the difference between V2 and the sum of two other signals?
Yes I DO understand HOW a summing (and differential) amp works........
If you understand HOW a summing amplifier works, what is SO difficult about seeing how to add a fifth resistor to the diff amp such that it is taking the difference between V2 and the sum of two other signals?