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Hi,
I have a design of an Op. Amp. in a follower configuration, made it for use in the previous stage of an ADC input. The circuit, is the following
The circuit was tested on another desing using the IC LMV324AIDR, and it work great.
On a new manufacture, the LMV324AIDR was out of stock, so I made the decision to replace it with the LMV324IDR (I check out all the datasheet, and I didn't notice any big difference) . When the boards arrive, I tested the circuit, and I notice that the output of the LMV324IDR have a saturation on a high level in 2.69 V aprox. (The Op. Amp. Supply it's 3.3V). Is these behaviour correct? I check the datasheet again and didn't find any information related to these issue.
BR,
Mauro
Hey Mauro,
It's also worth adding that the circuit as configured in the schematic violates the common mode voltage range of the device. 7 volts on that input divide divides down to 3.4V (outside your supply rails of either device).
Additionally the LMV324A can drive a larger capacitive load than it's non-a counterpart. Both datasheets go up to 1000pF with the A version above 20 degrees of phase margin, and the non-a version below 20 degrees PM. These are devices with different architectures (A is CMOS and non-A is bipolar), so they will have different output impedances. You may need to increase the size of your isolation resistor for stable operation.
Also, your output voltage swing from rail varies largely between these two devices.
Non-A version at 2.7V
Non-A version at 5V
A version Device
Best,
Jerry
Whether this was a good idea to give two totally different OPAmps the names "LMV324" and "LMV324A" only to be distinguished by the "A"?
Mauro,
as my previous speakers have already mentioned, as long as nothing is connected to "zone_1" the common mode input voltage range of LMV324 is heavily violated:
The datasheet of LMV324 says that the common mode input voltage must stay 1V below the supply voltage.
Kai
