Audio op-amps on +-12 V
An NE5532, an LM833 and an OPA2134 follow one knob from -12 V to +12 V: each stops where its data sheet says, 2 V, 1.2 V or 0.5 V short of a rail. There is no microcontroller in it: the simulator solves the 7 parts as a circuit, so it runs the moment you press Run, and nothing needs compiling.
Teaching? Assign it to your class in one click.
Intermediate About 20 minutes to build and run. Runs in your browser. Free, and no account needed.
The parts retail for about $10.30. On Mokxi they're free.
What you'll learn
- Dual supply (plus and minus 12 V) for op-amps
- Voltage follower: output tied to inverting input
- Output swing limits near the supply rails
- Reading differences between data sheets
- Measuring with several multimeters at once
- Difficulty: Intermediate
- Time: About 20 minutes
- Parts: 8
How it works
A 12 V supply and a -12 V supply power three audio op-amps: an NE5532, an LM833 and an OPA2134. A potentiometer between the two rails gives a knob that runs from -12 V to +12 V.
The knob feeds the non-inverting input of amplifier 1 in each chip. Each output is wired straight back to its inverting input, so each amp is a follower that copies the knob. Three multimeters read the three outputs.
In the middle of the knob all three match it. Near either end, each output stops short of the rail. The NE5532 stops about 2 V from both rails, at 9.99 V and -9.99 V. The LM833 and OPA2134 get closer.
Parts list
8 parts, plus the jumper wires and 3 bench instruments. The parts retail for about $10.30; on Mokxi they're free, and so are the instruments.
- 1 × Full-size breadboard
- 1 × Power, 12 V
- 1 × PotentiometerIn Halloween Prop Kit, Starter Projects Kit.
- 2 × Power, -12 V
- 1 × NE5532 dual audio op-amp
- 3 × Multimeter
- 1 × LM833 dual audio op-amp
- 1 × OPA2134 dual audio op-amp
Wiring table
Every connection, pin by pin, read from the circuit itself. Each row joins the pin on the left to the pin on the right, by a jumper wire or a breadboard strip.
| Part and pin | Connects to |
|---|---|
| Potentiometer pin 1 | 12 V |
| NE5532 dual audio op-amp pin VCC+ | 12 V |
| LM833 dual audio op-amp pin VCC+ | 12 V |
| OPA2134 dual audio op-amp pin VCC+ | 12 V |
| Multimeter (1) pin COM | Ground |
| Multimeter (2) pin COM | Ground |
| Multimeter (3) pin COM | Ground |
| NE5532 dual audio op-amp pin 1IN+ | Potentiometer pin 2 |
| LM833 dual audio op-amp pin 1IN+ | Potentiometer pin 2 |
| OPA2134 dual audio op-amp pin 1IN+ | Potentiometer pin 2 |
| Potentiometer pin 3 | -12 V |
| NE5532 dual audio op-amp pin VCC- | -12 V |
| LM833 dual audio op-amp pin VCC- | -12 V |
| OPA2134 dual audio op-amp pin VCC- | -12 V |
| NE5532 dual audio op-amp pin 1IN- | NE5532 dual audio op-amp pin 1OUT |
| Multimeter (1) pin V | NE5532 dual audio op-amp pin 1OUT |
| LM833 dual audio op-amp pin 1IN- | LM833 dual audio op-amp pin 1OUT |
| Multimeter (2) pin V | LM833 dual audio op-amp pin 1OUT |
| OPA2134 dual audio op-amp pin 1IN- | OPA2134 dual audio op-amp pin 1OUT |
| Multimeter (3) pin V | OPA2134 dual audio op-amp pin 1OUT |
The notes that come with it
There is no microcontroller in this one, so nothing is compiled: the simulator solves the circuit itself. The file in the editor is the notes that come with it.
// Three audio op-amps on +12 V and -12 V, each a follower of one knob.
//
// The knob runs from -12 V to +12 V. The meters read, left to right, an
// NE5532, an LM833 and an OPA2134 (amplifier 1 of each). In the middle all
// three copy the knob. Turn it to either end and each stops where its data
// sheet says its output stops:
//
// knob at +12 V knob at -12 V
// NE5532 9.99 V -9.99 V 2 V from both rails
// LM833 10.80 V -10.70 V 1.2 V and 1.3 V
// OPA2134 10.80 V -11.50 V 1.2 V and 0.5 V
//
// None of them is a single-supply part: on 5 V an NE5532 would have 1 V of
// room. They are made for +-9 V to +-15 V, where they are fast (12, 16 and
// 8 MHz) and quiet. The simulator does not model noise, so what tells them
// apart here is the swing.
Troubleshooting
The usual mistakes with this circuit, and the fix for each.
- A meter reads 0 V or nothing useful This project
Check that each multimeter COM is on ground and its V lead is on the matching op-amp output. - The op-amps do nothing with a single supply This project
These parts need both the 12 V and the -12 V rails. Connect the negative supply to every VCC- pin. - The reading jumps around or only covers part of the range. Potentiometer
Wire the two outer legs to 5 V and ground and the middle leg (the wiper) to an analog pin. Using the wrong two legs gives a dead or partial range. - Turning the knob does nothing, or the value is stuck at 0 or 1023. Potentiometer
Check that the wiper goes to an analog input (A0 to A5 on an Uno), not a digital pin. Make sure both ends are connected, since a floating end gives noise. - The output is clipped, distorted, or stuck at a rail. NE5532 dual audio op-amp
It is made for split supplies, such as plus and minus 5 V to 15 V. With a single supply, bias the inputs to half the supply with a divider and use coupling capacitors. - It oscillates or hisses. NE5532 dual audio op-amp
Decouple each supply pin with 0.1 uF close to the chip. Keep input leads short and do not leave unused inputs floating. Check pin 4 as negative supply and pin 8 as positive supply. - The reading is zero, negative or nonsense when measuring voltage. Multimeter
Set the dial to volts first, then touch the probes across the part, in parallel. Red goes to the more positive point. A negative number just means the probes are swapped. - Measuring current gives zero or blows the meter's fuse. Multimeter
Current must flow through the meter, so break the circuit and put the meter in series. Never put an amps setting straight across a supply. Start with the highest current range.
Change it and keep it
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