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Part Number: TLV274
Other Parts Discussed in Thread: OPA310

A few years back, we switched from TLV274CPW to TLV274IPW (industrial varsion). The circuit I have the opamp tied to is a reference signal or 4vdc (from an A/D). The op-amp is in a unitiy gain configuration. I use the 4v reference to power up some resistor pots. The total current output for all 4 drivers is 40ma. The output is of course 4vdc. The chip is powered with 5vdc +/-0.5vdc. 

When circuit is running the normal current is 24ma. When I push two resistor sensor buttons, the current draw goes up to 40ma. When I was using the TLV274CPW, the voltage out of the opamp is 4 volts (which is what it is supposed to be). When I pushed the two resistor buttons to add the extra load, the voltage remained the same (which is good). 

The issue I had was with the TLV274IPW (industrial device). At normal resting state (24ma), the voltage still read 4vdc. When I added the extra load though (16ma added which is equal to 40ma), the voltage dropped by 150mv. I don't think that is normal. According to the datasheet, it should be able to supply 100ma max. Has something changed?

  • That 100 mA value is the absolute maximum rating, i.e., the current at which the device can be damaged.

    As shown in figure 6, this device will not be able to output more than about 15 mA with a headroom of 1 V to the supply:

    The OPA310 would be strong enough.

  • Glenn,

    The input common mode maximum is VDD - 1.35V ; 4V with VDD at 5V is beyond the rated input common mode voltage. The high output drive capability and VCM range makes it surprising that it ever provided 40mA at 4V with VDD = 5V