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Author Topic: Need suggestion on single supply rail to rail op-amp to use with arduino uno?  (Read 2124 times)
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Can someone tell me a rail to rail op-amp that can be used with single supply 5V to 9V. Something easy and similar to LM358, also inexpensive.

I want a rail to rail op-amp that use single supply so that I can bais it somewhere at 2.5V and still get 0 to 5V using a battery. I have found a couple of op-amps, which are: TLC272, LT1466, LM324N, TLV2771, LM6144. What could be the best choice, or is there anything else that you suggest?

Thanks
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"Best choice" depends on your other criteria: cost? DIP or SMT? 1/2/4 op-amps per package? low noise? low input current? low offset voltage?

I usually start with the TLV2371 and look for other options only if that workhorse won't do the job for me. It's rail-to-rail input and output, works between 2.7V and 16V, has 3 MHz bandwidth, comes in 1/2/4 packages (TLV2371, TLV2372, TLV2374), comes in DIP and SMT versions, and has worst-case 6mV input offset voltage. It's also pretty cheap.

Usually it's the offset voltage that sends me looking for other op-amps, if necessary.

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1) Rail to rail mean, +ve to -ve voltage right?
2) If I want Gnd to +Vcc, can it be rail to rail?
3) I want to use gnd and +Vcc using a single supply battery, so whats the best option?
4) I want a single supply so that I can use gnd and +ve and bias in the positive region. So that the minimum would be 0V and maximum would be +Vcc.
5) I want an op-amp that can give me closest to +Vcc in this configuration.
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All your questions seem to be asking the same thing smiley  And the answer to all of them is "yes". A rail-to-rail input op-amp allows input voltages anywhere from V- (negative voltage supply of the op-amp) to V+ (positive voltage supply of the op-amp). A rail-to-rail output op-amp allows the output voltages to go all the way down to V-, and all the way up to V+ (well, within a few millivolts). A rail-to-rail input/output (RRIO) op-amp does both. The TLV2371 is RRIO.

This is why RRIO op-amps are often referred to as "single supply" since they can operate from just positive voltages and GND and don't need a negative supply rail to work with 0V at the inputs.

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1) By using TLV2371, I can bias at 2.5V and use from Gnd to +5V, right?
2) Whats the  maximum gain of TLV2371? I need maximum gain of 200 either with single op-amp (like lm386) or dual op amp (like lm 358)?

Thanks
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Is LM6142 a good choice. The datasheet for LM6142 says Gain 108dB with RL = 10k (so, does that mean I can achieve 100x gain with one op-amp of these)?

Thanks.
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Is LM6142 a good choice. The datasheet for LM6142 says Gain 108dB with RL = 10k (so, does that mean I can achieve 100x gain with one op-amp of these)?

Thanks.

Yes, 100X gain is only +20db gain, easily done with most any modern op amp for DC and lower AC frequencies. The 108db gain figure is the open circuit (when using no negative feedback) gain and is not really a usable figure in most application except possibly when used as a comparator.


« Last Edit: January 07, 2012, 05:53:58 pm by retrolefty » Logged

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Quote
1) By using TLV2371, I can bias at 2.5V and use from Gnd to +5V, right?

Right.

Quote
2) Whats the  maximum gain of TLV2371? I need maximum gain of 200 either with single op-amp (like lm386) or dual op amp (like lm 358)?

I think you are confusing an "op amp" with an "audio amplifier". Devices like the LM386 are pre-built audio amplifiers with a certain gain. A regular op-amp like the TLV2371 has to be designed in a certain configuration (inverting amplifier, non-inverting amplifier, etc.) and you select the gain by your choice of resistors in the circuit. Here is a good place to start reading:

http://en.wikipedia.org/wiki/Op_amp#Negative_feedback_applications

The LM6142 should work too, but we can't comment on whether or not it's a good choice unless you have more specifications. What's wrong with the TLV2371? It's a lot cheaper than the LM6142 (5 times cheaper by my estimate).

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