| Electronics > Beginners |
| Op amp selection help. |
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| BradN:
I am looking for a rail to rail opamp with a 10v or 12v single supply in a dip package. I need this to amplify the signal from a MCP4727 DAC to 10V to control a piece of machinery that requires 0-10v control signal. I have little experience with analog electronics and have been wading through rivers of opamp data sheets and am still not sure if I am selecting the correct devices. Any suggestions would be appreciated. |
| Kleinstein:
A common RR op for up to 16 V is the TS912, though only dual version available. If the supply is 12 V or higher, one might get away with a single supply OP, maybe even an LM358 (with a light load). |
| Simon123:
Or maybe just use Voltage inverter to get the negative rail, ICL7650 for example and then use OP07 or TL071 or something ... |
| rstofer:
One of the first things you need to know is the input impedance of the load. Sure, you have to send 0-10V but at what current? It could be quite high and of no concern. But it might not be... Then, since bandwidth is not likely to be an issue, any op amp can do the job. Rail-to-rail is often a marketing term. Given a supply of 0V-15V I'm not sure that you can actually get down to 0V on the output for 0V on the input. There simply must be some voltage drop across the output driver. Given that the supply voltage is higher than the required output (15V supply, 10V signal) there should be no problem on the top end. I would avoid working at the edges. If necessary, I might use -2V +12V for the supply voltages to leave a bit of room at the rails. I wouldn't mind throwing out the negative side and using the far more common -15V..+15V supplies. Or even -12V..+12V. |
| Zero999:
--- Quote from: Kleinstein on September 16, 2018, 03:55:28 pm ---A common RR op for up to 16 V is the TS912, though only dual version available. If the supply is 12 V or higher, one might get away with a single supply OP, maybe even an LM358 (with a light load). --- End quote --- It also depends on whether the load sinks or sources current. The LM358's output can't get very near zero, if the output has to sink more than 10µA. If the load is just a 1k resistor to 0V, then it should be fine, as it will only need to source current and 10V out at 10mA, with 12V in is no problem for the LM358. If only one op-amp is required, it's also possible to connect the two op-amps in the LM358 in parallel, to increase the output drive. https://www.intersil.com/content/dam/Intersil/documents/an11/an1111.pdf |
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