Hello,

I'm just starting to learn about op amps and I'm experiencing some strange behavior with the NE5534. My actual goal is to do some very simple audio amplification, but I boiled the problem down to the circuit in the attached schematic. What I'm expecting is that the output voltage should be roughly 11 times the input voltage, because of the non-inverting configuration. I built the same circuit with an LM358 and I observed what I expect. But with the NE5534 I'm reading 5V when the input is 0V, and the output voltage goes up to about 11.5V as I increase the input voltage. Can anyone explain this to me? I realized that I haven't connected pins 1,5, and 8, but as I understand it, this should only be necessary for fine-tuning the op amp or for low gains (less than 3).

Thanks!

 

Not all opamps are created equal. The LM358 has what was in 1970 a ground-breaking input stage, where as the 5534 has a more conventional input stage. Check both datasheets for the common mode input voltage range. The 358's extends below the negative rail, while the 5534'3 does not. So when the input voltage in your circuit gets down to around 1.5 V or less, the 5534 enters no man's land. The 5534 also does not have as large an output voltage swing range, especially when pulling down toward the negative rail. Much of this is because the 358 was designed as an opamp that can talk directly to digital chips in the 7400 TTL series, while the 5534 is intended for classic, dual power supply, analog stuff. The 5534 has better gain, better distortion, better noise, etc., but it is relatively hungry and does have some personality quirks.

ak

 

Thanks for the reply! The datasheet for the 5534 says that it has a common mode input range of +/- 12 V for a supply voltage of +/- 15 V. Does that mean that the input range is always 3 V below / above the supply voltage range? So, in case of my 12 V single-supply example, would the inputs have to be in the range of 3 V to 9 V? The solution to my problem would then be to offset both inputs by at least 3 V -- is that correct? Would it be fair to say that the 5534 is not the best choice for single-supply operation becasue neither rail is included in the input range?

Thanks!

 

Thanks for the reply! The datasheet for the 5534 says that it has a common mode input range of +/- 12 V for a supply voltage of +/- 15 V. Does that mean that the input range is always 3 V below / above the supply voltage range? So, in case of my 12 V single-supply example, would the inputs have to be in the range of 3 V to 9 V? The solution to my problem would then be to offset both inputs by at least 3 V -- is that correct? Would it be fair to say that the 5534 is not the best choice for single-supply operation becasue neither rail is included in the input range?!

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Grand Slam.

ak

 

Thanks for the reply! The datasheet for the 5534 says that it has a common mode input range of +/- 12 V for a supply voltage of +/- 15 V. Does that mean that the input range is always 3 V below / above the supply voltage range? So, in case of my 12 V single-supply example, would the inputs have to be in the range of 3 V to 9 V? The solution to my problem would then be to offset both inputs by at least 3 V -- is that correct? Would it be fair to say that the 5534 is not the best choice for single-supply operation becasue neither rail is included in the input range?

Thanks!

You also have to decide what/how you'll want to really get a signal out of this circuit?

The output is 11x the input voltage. So, with a NE5534, you can have an input somewhere between 3/11 and 9/11 volts. That is 0.3 and 0.9 volts. Which is outside the input/output range of the op amp.

If you get an op amp with rail to rail output (and input), then your input could range from 0 to 12/11 volt (1.1 v).

You'll have to, as you suggested, get some biasing in place to get the output swing that you want and possibly some capacitive coupling of your signal.